Wednesday, 6 December 2017

50 TOP Irrigation Engineering Interview Questions & Answers pdf

Here are top 50 Irrigation Engineering Interview questions and answers are given just below to them. These sample Irrigation Engineering questions are framed by experts. who train for Learn Irrigation Engineering Online to give you an idea of Irrigation Engineering questions which may be asked in interview. We have taken full care to give correct answers for all the questions. Do comment your thoughts. Happy Job Hunting!

1. Why Are Landscapes Irrigated?
Simply stated, irrigation provides the water requirements for sustainability of plants when rainfall is not sufficient.
Ornamentals: Trees and shrubs are irrigated frequently when grown in the nursery and when first planted so that their roots quickly grow out from the root ball and into the soil in the landscape. It is crucial that roots grow as quickly as possible so irrigation can cease. The best way to encourage rapid root growth is frequent light irrigation applied to the root ball after planting. Under ideal conditions (e.g., in non-compacted soils, surrounded by extensive irrigated areas), many Florida-Friendly plants do not require further irrigation except in prolonged drought.
Turf: Although Florida receives substantial rainfall, dry periods are common in the late spring and fall. The dry period in the spring coincides with peak plant water needs due to increasing temperatures, solar radiation, and day length. Due to relatively shallow roots, turfgrasses typically require irrigation at least once a week to maintain quality. On sandy soils, some grasses may need to be irrigated at least two days a week to ensure acceptable quality (Shedd et al., 2008).

2. What Are The Irrigation Requirements For Turfgrass And Landscape Plants?
Note: The term “irrigation requirements” implies well-watered conditions, which means that this is the amount of irrigation water in addition to effective rainfall (that which is stored in the plant root zone and available for use) needed for plant growth and without any water stress.
Ornamentals: All landscape shrubs and trees grown in a nursery and planted in a landscape require water to become established. Under most circumstances, rainfall occurs irregularly, so irrigation is required, at least until plants are established. Trees require about three to four months per inch of caliper (trunk diameter measured 6" from ground) to become established. Shrubs require about 20 to 28 weeks to become established. Irrigation events should be 2 to 3 gallons of water per inch trunk diameter. For example, a 2-inch tree should be watered 4 to 6 gallons at each irrigation event. Water every other day until plants are established.
In addition to initial watering for establishment, irrigation in the year following establishment may be needed to maintain good quality in dry weather. We have little data on irrigation requirements for plants once established, due to the many factors that influence this. These factors include slope, aspect, soil compaction, soil depth, soil volume, width of soil space, depth to water table, wind, season, size of plant at planting, nursery production method, length of time in the container, and root pruning strategies at planting. This research simply has not been done.
Turf: Under well-watered conditions, Stewart and Mills (1967) reported that annual water consumption in South Florida for St. Augustinegrass and bermudagrass averaged 43 inches/yr over five years. For North Florida, Jia et al. (2007) reported 33 inches of total water requirements for bahiagrass. Irrigation requirements for turfgrass in North Florida are on the order of 20–25 inches/yr and 30–35 inches/yr in South Florida, on average (Smajstrla, 1990). These numbers are net irrigation requirements and do not include added irrigation due to the inefficiency inherent in all irrigation systems. See “Efficiencies of Florida Agricultural Irrigation Systems, ” for more information on irrigation efficiency (Smajstrla et al., 1991). In most years, rainfall will contribute substantially to meeting the total water demand of turfgrasses.

3. Do Different Varieties Of Turfgrasses Use Different Amounts Of Water?
Many studies have been conducted on water use of turfgrasses. Most of these studies are conducted under “well-watered” conditions (i.e., no stress due to lack of water) and should not be confused with drought studies where water is withheld and physiological responses of grasses are studied.
All turfgrasses need water to sustain good quality (dense, uniform, green), whether it comes from rainfall or supplemental irrigation. Drought-tolerant grasses will go into dormancy during dry periods, growing more slowly or turning brown until conditions are favorable for growth. When enough soil moisture returns, these grasses can usually recover from drought-induced dormancy rather than dying. For example, bahiagrass is drought-tolerant, but if it is not supplied with adequate water, the drought response of this grass will result in dormancy and a “dead” appearance.
Much of the literature seems to indicate that there may be differences in water use between different warm-season grasses. These disparities likely stem from natural differences in mowing heights (e.g., St. Augustinegrass lawns versus bermudagrass golf turf), fertility, leaf architecture, etc. However, these differences have not been clearly documented in Florida work.
In one study, Zazueta et al. (1999) found that when maintained under UF/IFAS recommendations, bahiagrass had 11 percent higher water use rates than St. Augustinegrass when well-watered, but that the two grasses had similar transpiration rates when under continual stress. A current UF/IFAS study is exploring the water use rates, under well-watered conditions, of several grasses including St. Augustinegrass and bahiagrass.

4. Do Natives Require Less Water? If So, When?
A plant's indigenous status does not affect its fertilizer or irrigation requirements. There is no scientific evidence that native plants require less fertilizer and water than plants not native to Florida. To put it another way, residential and commercial landscapes are often very different from the native conditions where a plant originated, even if they are found in the same state. Additionally, a plant that was previously indigenous to a site may not be adapted to the location any longer, depending on the way the site has been altered. In a recent research study, Florida native shrubs required the same irrigation as non-natives (Scheiber et al., 2007). Fertilizer requirements have not been tested.

5. Will Planting Another Type Of Turfgrass Automatically Result In Water Savings?
The scientific evidence seems to point to human behavior with regard to over-irrigation—not particular plants in the landscape—as the reason for much wasted irrigation water. In addition, there is some evidence that in well-watered (i.e., sustained good quality) conditions, bahiagrass uses slightly more water than St. Augustinegrass. Thus, replacing St. Augustinegrass with bahiagrass will not likely reduce water needs for well-watered conditions. In addition to water, there are many other factors, such as maintenance level, diseases, and pests, that need to be considered related to a turfgrass change.

6. What Is The Proper Way To Irrigate?
Scientifically, irrigation should occur based on plant response to environmental demand. Thus, irrigation frequency and amount will be defined by the environmental demand (i.e., evapotranspiration, ET), soil water-holding capacity and plant root zone depth. Irrigation should be applied such that the soil water reservoir is filled and gravity drainage and runoff do not occur. This approach is detailed in an EDIS publication entitled, “Basic Irrigation Scheduling in Florida,” (Smajstrla et al., 2006), which provides summary information from internationally recognized publications such as “Crop evapotranspiration: Guidelines for computing crop water requirements” (Allen et al., 1998). This scientifically accepted approach aims to result in “well-watered” conditions where no stress is allowed. In addition, an irrigation system must be well-designed and in good repair to apply irrigation efficiently to plants (i.e., without losses due to runoff and deep percolation).
In practice, irrigation is often limited to specific days of the week by water management districts through most of Florida. Thus, landscape plants may undergo varying levels of stress depending on specific site conditions and plant type.
Ornamentals: In the case of newly planted trees and shrubs, water should be applied to the root ball and perhaps the soil just beyond the root ball. In all of the studies over the past twenty-two years on trees in Florida, the area beyond the root ball has not been irrigated. Trees and shrubs establish just fine without broad, landscape-wide (i.e. sprinkler) irrigation. For example, live oak and southern magnolia tree root systems extend to about 14–20 feet in diameter one year after planting in a non-compacted soil without interference from curbs, sidewalks and other soil obstructions.
Turf: Guidelines for turf irrigation include an irrigation system that is well designed and in good repair. Generally, UF/IFAS irrigation guidelines recommend irrigation of ½–¾ inches when 30–50 percent of turfgrass shows signs of wilt during the day. However, if an automatic irrigation system is used under day-of-the-week water restrictions, program run time recommendations are given in “Operation of Residential Irrigation Controllers.” The recommendations in this publication have been further refined into user-friendly guidelines and posted as the FAWN urban irrigation scheduler.

7. Are The Terms “drought-tolerant” And “irrigation Requirement” Related?
Physiologically, tolerance means that the organism tolerates the stress without suffering major damage or is able to continue to function in a stress-induced state. Plants may do this through drought avoidance, physiological adaptations that afford tolerance, or through efficiency mechanisms. Drought avoidance may be escape, such as a plant that reproduces quickly, thereby avoiding drought, or through conservation mechanisms such as stomatal closure, change in leaf canopy or orientation, or cuticular resistance. They may also avoid drought by developing an extensive root system.
Physiological adaptations may include osmotic adjustment, changes in cellular elasticity, and dessication tolerant enzymes, all of which help the plant maintain turgor. Efficiency mechanisms include high water use efficiency (WUE). WUE is often defined as growth per units water provided, photosynthesis per units water, etc. Mechanisms that enhance drought tolerance reduce WUE because growth and carbon assimilation are reduced by leaf firing, rolling, etc.
It is important to note that any plant will require frequent irrigation after planting to ensure survival and establishment. For established plants, the irrigation requirement is defined as the water needed, exclusive of rainfall, for a crop to grow without water stress. It is the difference between ET (evapotranspiration or plant water use) and rainfall. ET may be calculated using one of a number of models, all of which have inherent uncertainty. Using climatological data, one can estimate ET and thus calculate the irrigation requirement on a monthly or annual basis as the difference between ET and effective rainfall. Effective rainfall is rainfall that is estimated to remain in the root zone of the plant. Effective rainfall is the result of total rainfall minus losses to drainage and percolation below the root zone.
Ornamentals: Once drought-tolerant plants, like live oak and burford holly, are established, they can withstand extended dry periods with little or no irrigation.
Turf: All of our grasses in Florida use different mechanisms to go into dormancy during drought stress (leaf firing, rolling, etc.). This metabolic resting state allows them to survive the stress and some of them to resume growth after conditions again become favorable.

8. Can Reclaimed Water Be Used For Irrigation?
Yes, reclaimed water can be and is used for irrigation. In fact, Florida is a leader in the U.S. in the use of reclaimed water for irrigation, with approximately 660 million gallons of reclaimed water being used each day, according to the Florida Department of Environmental Protection 2006 Reuse Inventory.
Reclaimed water does typically contain elevated levels of salts relative to Florida surface and groundwater, except where saltwater intrusion is problematic in coastal areas. The elevated levels of salts in reclaimed water may impact different plant species in varying ways due to differences in salt tolerance. Periodic testing of reclaimed water used in irrigation is recommended.
Also, reclaimed water may contain plant nutrients, which may need to be considered in any fertility program. It is not clear that all the nutrients in reclaimed water are available for plants. Finally, the content of reclaimed irrigation water can vary between different municipalities due to permitting differences and specific differences between wastewater treatment plants.

9. Is There A Correlation Between Plant Water Need And Homeowner Water Use?
Haley et al. (2007) showed that homeowners did use significantly less water in the winter than other seasons. However, overall homeowners over-watered as much as 2–3 times the amount needed by the plants, based on estimates of climate demand. Thus, there is some indication that homeowners reduce irrigation during periods when less is needed; however, it appears that over-irrigation may still occur.

10. Are Day-of-the-week Restrictions Effective At Reducing Water Use?
In a word, yes, but only if they are enforced. Over time, their effectiveness can become reduced. Olmsted (2008) reviewed the literature to determine the effectiveness of day-of-the-week watering restrictions specific to Florida. In Hillsborough and Orange Counties, water use reductions (by utilities) were reported as 17–18 percent; however, no reductions were seen in Seminole County. In South Florida, day-of-the-week restrictions reduced water use up to 21.5 percent during one day/week watering restrictions.
Day-of-the-week restrictions limit flexibility for users who try to plan irrigation based on rainfall trends. In addition, they may encourage over-watering on the allowed day. Just because potable water demands decrease under restrictions, it doesn't mean that irrigation is being applied at the right time and in the right amount—in other words, it's possible that water is still being wasted, even though it may be a smaller amount. However, to a large extent, many landscape plants can survive during most periods of water restriction.

11. Are There Uf/ifas Recommendations For Irrigation, And, If Followed, Do They Provide Water Conservation Benefits?
Ornamentals: Irrigation recommendations for trees can be found at There is no documentation of how many people follow them. It would be difficult to document the effect of specific practices on ornamental plant material, since these materials only make up part of the planted landscape in most cases. Further, in many irrigation systems, turfgrass and ornamentals and trees are not separated in terms of irrigation zones and thus receive the same amount of irrigation relative to the system programming.
Turf: UF/IFAS recommends watering when 30–50 percent of turfgrass wilts. This should provide water conservation benefits relative to “set it and forget it” time clock programming; however, this has not been documented.
Haley et al. (2007) showed that using the schedule recommended in “Operation of Residential Irrigation Controllers ” reduced watering by 30 percent over a thirty-month study. Thus, if this recommendation were followed, substantial water savings are possible for moderate to high irrigators. The “FAWN urban irrigation scheduler " uses these recommendations in a user-friendly fashion to encourage users to adjust irrigation time clocks to better adjust for climatic demand throughout the year.

12. Which Turfgrasses And Landscape Plants Can Be Grown Without Supplemental Irrigation Or Fertilization?
Some turf species may not need water to survive, but all need water to stay green. Drought tolerance implies that the grasses will “fire” (turn brown) and reduce leaf area to conserve water. Some, such as bahiagrass or centipedegrass, will exhibit better recovery from drought stress. St. Augustinegrass and most of the zoysiagrass varieties will not generally persist well without supplemental irrigation during times of limited rainfall. Fertilization follows a similar trend—bahiagrass and centipedegrass have low fertilization requirements and can persist with relatively low levels of nutrients.

13. What Are The Mechanisms Available To Reduce Over-watering Right Now On Existing Irrigation Systems In Landscapes? How Effective Are These Mechanisms?
Florida statute 373.62 mandates the installation of a working rain sensor device or switch on all automatic irrigation systems installed since 1991. UF/IFAS research has shown that expanding disk rain sensors can be effective at conserving water. Potential savings of 17 to 34 percent were shown at ½-inch and ¼-inch thresholds under normal rainfall frequencies (Cardenas-Lailhacar & Dukes, 2008; Cardenas-Lailhacar et al., 2008).
Ornamentals: In 22 years of irrigation research on trees and shrubs, only drip irrigation and other low-volume irrigation devices have been used. These devices have allowed very little water application while maintaining plant quality, though there are issues with pests such as squirrels chewing through the lines, causing maintenance problems.
Turf: Cardenas-Lailhacar et al. (2008) showed that technology such as soil moisture irrigation controllers can reduce irrigation by 70–90 percent for a range of products and irrigation watering days without negatively impacting turf quality during normal rainfall conditions. Further work with properly installed soil moisture sensor irrigation controllers on homes in Florida shows the potential for 50 percent irrigation savings without a negative impact on landscape quality (Haley & Dukes, 2007). Similar savings appear possible with other “smart irrigation” controllers such as ET controllers.

14. What Is Drip Irrigation?
Drip irrigation is the process of delivering precise amounts of water and nutrients directly to the plant's root zone, drop by drop, offering growers exact irrigation control and efficient use of limited water resources.

15. Why Should I Use Drip Irrigation?
Slow even flow of water to plants and soil: Shrubs and plants will thrive. Application of water and nutrients directly to the plant's roots is the best way to ensure plant health and vitality.
Easy to install - flexible and daptable: Dripperline installs easily in tight, awkwardly shaped areas that are hard to water with conventional spray systems.
Solves spray irrigation: problems No damaging spray on buildings, windows, fencing, or pedestrians in high traffic areas.   Avoids unsightly brown spots on roses and other flowers, since spray never touches the plants. Soil and foliage are kept dry, reducing fungal diseases.
Improved plant growth: Makes plants fuller and healthier. Water and nutrients delivered directly to the root zone promotes healthy plant growth and reduces plant stress. Soil aeration is improved because soil particles are not washed down, decreasing soil compaction and improving root growth.
Saves on maintenance & labor: No moving sprinkler parts to have to repair.  Installs with far less labor than sprinklers.
Unobtrusive & aesthetic: Hidden and lying near the plant, colored  Brown. Doesn't interfere with landscaping or scenery.
Security: No exposed sprinkler heads, pipes or surface dripperlines to trip on or tamper with.  

16. Where Should I Use Drip Irrigation?
You'll be delighted with the fuller blooms and greater beauty of your annuals and perennials when watered. Mature plants and shrubs grow fuller and healthier with dripperline's versus sprinkler watering.

17. Why Micro Irrigation Is Necessary?
To improve the productivity of irrigated land from the present low levels.
To improve use-efficiencies of Water, Energy, Nutrient and Human Effort in Agriculture.
To conserve scarce resources such as Water and Electricity.
To extend the benefits of irrigated agriculture to more people with the available water.
To facilitate better crop management through Fertigation and Chemigation

18. What Are The Advantages Of Micro Irrigation?
Crop Yield Enhancement
Saving in Irrigation Water
Saving in Energy in pumping
Savings in Fertilizer consumption
Quality Improvement of Produce
Improved Pest & Disease Control
Improves Soil Health
Reduced Weed Growth
Reduced Labor Costs
Suitable for Marginal lands
Suitable for inferior quality water

19. What Is Subsurface Drip Irrigation (sdi)?
When a drip tape or tube is buried below the soil surface, it is less vulnerable to damage during cultivation or weeding.  With SDI, water use efficiency is maximized because there is even less evaporation or runoff.

20. What Is Sprinkler Irrigation?
Sprinkler Irrigation is a method of applying irrigation water which is similar to rainfall. Water is distributed through a system of pipes usually by pumping. It is then sprayed into the air and irrigated entire soil surface through spray heads so that it breaks up into small water drops which fall to the ground.
Sprinklers provide efficient coverage for small to large areas and are suitable for use on all types of properties. It is also adaptable to nearly all irrigable soils since sprinklers are available in a wide range of discharge capacity.

21. What Is Microirrigation System?
Microirrigation is frequent application of water directly on or below the soil surface near the root zone of plants. It delivers required and measured quantity of water in relatively small amounts slowly to the individual or groups of plants. Water is applied as continuous drops, tiny streams, or fine spray through emitters placed along a low-pressure delivery system. Such system provides water precisely to plant root zones and maintains ideal moisture conditions for plant growths.

22. Types Of Microirrigation System?
The basic types of microirrigation system are as follows:
Surface System: It is the system in which emitters and laterals are laid on the ground surface along the rows of crops. The emitting devices are located in the root zone area of trees.
Sub-surface System: It is a system in which water is applied slowly below the land surface through emitters. Such systems are generally preferred in semi permanent/permanent installations.
Bubbler system:  In this system the water is applied to the soil surface in a small stream or fountain. Bubbler systems do not require elaborate filtration systems. These are suitable in situations where large amount of water need to be applied in a short period of time and suitable for irrigating trees with wide root zones and high water requirements.
Micro and mini Sprinklers: These are small plastic sprinklers with rotating spinners. The spinners rotate with water pressure and sprinkle the water. These are available in different discharges and diameters of coverage and can operate at low pressure in the range of 1.0 to 2kg/cm2. Water is given only to the root zone area as in the case of drip irrigation but not to the entire ground surface as done in the case of sprinkler irrigation method.
Pulse:  Pulse system uses high discharge rate emitters and consequently has short water application time.  The primary advantage of this system is a possible reduction in the clogging problem.
Biwall: It is extruded dual chamber micro-irrigation tubing manufactured from Linear Low Density Polyethylene (LLDPE). This system is suitable for all closely spaced row crops like sugarcane, cotton, vegetables, onion, tea etc.

23. How About Those Tight Or Awkwardly Shaped Areas That Are Difficult To Water With Conventional Spray Systems?
Dripper lines solve the problem and avoid spraying your walls, window and fences. Consistent watering with dripper lines helps establish and protect new shrub beds and planting areas.

24. Can I Save Money Using Drip Irrigation Vs. Traditional Spray Sprinklers?
It is frequently more profitable to install a systems when you are dealing with long, narrow strips, awkwardly shaped areas, or tree, shrub and bedding plant areas - both from a materials cost and labor standpoint. To help the minimize liability and vandalism and saves your customers' costs associated with continued maintenance and water usage.  A simple shrub bed installation is quick and easy, either buried 4" below the surface or beneath mulch.

25. What About Different Soil Types? Even Clay?
Subsurface irrigation works better in heavy clay or sand conditions than traditional sprinkler systems. Even "heavy clay" and "sandy" soils are a mixture sand, silt and clay. Loam, which contains equal proportions of sand, silt and clay, is ideal. However, plants can thrive in a very broad spectrum of soil textures when subsurface watering is applied at the proper rate, with appropriate spacing. Different soils create typical wetting pattern shades as seen at right. Note the dramatic overlap ensuring total coverage throughout varying root zone depths.
Drip irrigation works great in clay soils. What most people regard as "heavy clay" and "sandy" soils are actually mixtures of sand, silt and clay which will allow for adequate water movement and retention between soil particles.

26. Does Water Only Move Downward, Pulled By Gravity?
When applied slowly (as in drip irrigation) water radiates outward from its source point, creating an overlapping wetting pattern beneath the ground. See the "wetted pattern" illustration" at right. When applied slowly to the soil at a single point, water moves through the soil in two ways:
Downward pulled by gravity.
Outward and upward, pulled by a capillary action.

27. How Can I Tell The System Is Working?
There are several ways to verify that your system is working, including:
Feel for moisture just below the surface of the soil directly above a dripper.
Run micro tubing to the surface at the end of a zone and use it as a point source dripper.
Install a flag indicator at the end of zone.
Monitor flow at the water meter.
Because water travels both upward and outward from the dripper, the soil will usually be damp at, or close to, the surface.

28. Will An Automatic Sprinkler System Use More Water Than I'm Currently Using?
No. In fact, it will conserve water. The system's controller and rain sensor will be set so you receive only the amount of water you need. You will not over-water or under-water your lawn with an automatic sprinkler system.

29. Does Having A Sprinkler System Really Save Time?
Yes. You won't have to spend another minute of your valuable leisure time watering the lawn. Whether you are home or away your system will do the watering for you!

30. Will Automatic Sprinkler System Water As Well As I Can Water By Hand?
It will do a much better job because a professionally designed system will deliver exactly the right amount of water to individual lawn and garden areas.

31. We Generally Get 40 Or More Inches Of Rainfall A Year. Do We Really Need A Sprinkler System?
If it rained at your house every three days the same exact amount each time you probably would not need a sprinkler system. But nature does not work that way, and the only way to ensure healthy, lush growth is to make certain your lawn and plants receive a regularly timed, evenly measured amount of water. In the dry season when there is little or no rain, your yard can suffer damage after just a few days without water.

32. How To Protect The Drip System From Rat?
By providing raised beds over the laterals.

33. Emitter Is Not Functioning Well, Why?
It’s due to some fine particles clogging the emitter because of bad quality of water. In that case we should provide filtration unit for removing fine particulars present in the water.

34. How Much Subsidy Government Gives For Installation Of Drip System?
50 % of installation drip irrigation cost as given as subsidy by the government.

35. Which Type Of Mulching Material Is Useful For Controlling Weeds?
Normally Black polythene film is recommended for controlling weeds.

36. How To Clean The Drip System?
Open all end caps in lateral; main and submain pipes and operate the motor at least ten minutes to remove all fine particles presents in drip irrigation system.

37. How To Reduce The Drip System Cost?
In Paired row system, the total number of lateral is less comparing to single row system.  Total cost of unit will reduce by adopting this method.

38. How Much Depth Is Needed For Laying Sub Main In The Field?
Normally we recommended 60-70 cm from the top of the soil.

39. Venturi Is Not Working Well, Why?
There is less pressure in pressure gauge or leaking problem in venturi system or pump is not functioning well.

40. Why Water Is Not Flowing Upto Lateral End?
Because of holes, bents and cuts in laterals. To avoid this close the holes and cut and remove the bends present in the laterals.

41. While Removing The End Plug White Mixture Is Coming. Why?
This is due to uncleaned lateral and more salinity in water. This can be avoided by cleaning the laterals fortnightly.

42. Some Times Oily Gum Material Comes Out On Opening The Lateral End. Why?
Presence of more algae or ferrous material in water. Clean the laterals with water or give chemical treatment.

43. Why Pressure Gauge Is Not Working Some Times?
Rain water entry inside. Corrosion in gauge pointer damage. Provide plastic cover and fix pointer properly.

44. How Drop In Pressure Occurs?
Leakage in main opened outlet and low water level in well. Arrest the leakage and close outlet and lower the pump with reference to well water level.

45. What Is The Reason For More Pressure At The Entry Of Sand Filter?
Provide bypass before filter and regulate pressure. Place filter element properly. Fill required quantity of sand.

46. Leakage Of Water From Air Release Valve. Why?
Due to damaged air release valve ring. Replace the damaged ring.

47. Suitable Crops For Drip Irrigation?
All vegetable crops, Flower and fruit crops and Tree crops.

48. Suitable Crops For Sprinkler Irrigation?
Lemongrass, Groundnut, Pulses, Sugarcane and Tubercrops.

Also Read 50 Irrigation, Water Resources Engineering MCQs

TOP 20 Tunnel Engineering Interview Questions & Answers pdf

Here are top 20 Tunnel Engineering Interview questions and answers are given just below to them. These sample Tunnel Engineering questions are framed by experts. who train for Learn Tunnel Engineering Online to give you an idea of Tunnel Engineering questions which may be asked in interview. We have taken full care to give correct answers for all the questions. Do comment your thoughts. Happy Job Hunting!

1.  What is the difference between network gateway and a firewall?
A network gateway joins two networks together and a network firewall protects a computer network against unauthorized incoming or outgoing access. Network firewalls may be hardware devices or software programs.

2. What is the difference between IPS and a firewall? 
The primary function of a firewall is to prevent/control traffic flow from an untrusted network (outside). A firewall is not able to detect an attack in which the data is deviating from its regular
pattern, whereas an IPS can detect and reset that connection as it has inbuilt anomaly detection.
Tunnelling - Civil Engineering Questions and Answers
3. What is a transparent firewall? 
A transparent firewall is considered as Layer 2. Deploying a new firewall into a network can be a complicated process due to various issues (e.g. IP address reconfiguration, network topology
changes, current firewall etc.) because the firewall is not a routed hop and you can easily introduce a transparent firewall into an existing network.

4.What is packet filtering?
Packet filtering is the process of permitting or blocking ip packets based on source and destination addresses, ports, or protocols. The packet filter examines the header of each packet based
on a specific set of rules, and on that basis, decides to prevent it from passing or allow. Packet filtering is also part of a firewall program for protecting a local network from unwanted access.

5.Define stateful inspection?
Stateful inspection is known as dynamic packet filtering and is a firewall technology that monitors the state of active connections and uses this information to determine which network packets
are allowed through the firewall. Stateful inspection analyses packets down to the application layer

6. What is the Public Key Encryption? 
Public key encryption uses public and private key for encryption and decryption. In this mechanism, public key is used to encrypt messages and only the corresponding private key can be
used to decrypt them. To encrypt a message, a sender has to know the recipient’s public key.

7. What is Authorization? 
Authorization is a security mechanism used to determine user/client privileges or access levels related to network resources, including firewalls, routers, switches and application features.
Authorization is normally preceded by authentication and during authorization. It’s system that verifies an authenticated user’s access rules and either grants or refuses resource access.

8. What is stateful failover?
Every time a session is created for a flow of traffic on the primary node, it is synced to the secondary node. When the primary node fails, sessions continue to pass traffic through the secondary node without having to re-establish.

 9. What is Site to Site and remote access VPN?
A site-to-site VPN allows offices in multiple locations to establish secure connections with each other over a public network such as the Internet. Site-to-site VPN is different from remote-access VPN as it eliminates the need for each computer to run VPN client software as if it were on a remote-access VPN.

10. How do you check the status of the tunnel’s phase 1 & 2 ? 
Use following commands to check the status of tunnel phases:
Phase 1 : show crypto isakmp and State : MM_ACTIVE
Phase 2 : show crypto ipsec sa
Note: if you have lot of tunnels and the output is confusing use a ‘show crypto ipsec sa peer’ command instead.

11. What is SSL VPN? How it is different from IPsec VPN?
SSL VPN provides remote access connectivity from almost any internet enabled location without any special client software at a remote site. You only need a standard web browser and its native SSL encryption.
IPsec is a dedicated point-to-point fixed VPN connection where SSL VPNs provides anywhere connectivity without any configuration or special software at remote site.

12. What is GRE and why is it required?
Generic Routing Encapsulation (GRE) is a protocol that encapsulates packets in order to route other protocols over IP networks.
GRE enables a wrapper to be placed around a packet during transmission of the data. A receiving GRE removes the wrapper, enabling the original packet to be processed by the receiving stack.
Advantages of GRE tunnels include the following:
GRE tunnels connect discontinuous sub-networks.
GRE tunnels allow VPNs across wide area networks (WANs).
GRE tunnels encase multiple protocols over a single-protocol backbone.
GRE tunnels provide workarounds for networks with limited hops.

13. Firewalls work at what layer? Define firewall generations and their roles.
Firewalls work at layer 3, 4 & 7. First generation firewalls provide packet filtering and they generally operate at layer 3 (Network Layer). Second generation firewalls operate up to the Transport layer (layer 4) and records all connections passing through it and determines whether a packet is the start of a new connection, a part of an existing connection, or not part of any connection.
Second generation firewall is mainly used for Stateful Inspection.
Third generation firewalls operate at layer 7. The key benefit of application layer filtering is that it can “understand” certain applications and protocols (such as File Transfer Protocol (FTP),
Domain Name System (DNS), or Hypertext Transfer Protocol (HTTP)).

14. What is DoS attack? How can it be prevented?
DoS (Denial of Service) attack can be generated by sending a flood of data or requests to a target system resulting in a consume/crash of the target system’s resources. The attacker often
uses ip spoofing to conceal his identity when launching a DoS attack.
- The data is split into smaller packets and passed through the tunnel.
- The data passing through the tunnel has 3 layers of encryption. The data is encapsulated.
- Tunneling can be approached by Point to Point tunneling protocol.
- It allows the private network communication to be sent across a public network.
- The encapsulation process allows the data packets to appear as they are of a public nature in the public network.
- It is also known as port forwarding.

=> Also Read Tunnel Engineering MCQs

20 TOP Structural Analysis Interview Questions and Answers pdf download

Here are top 200 Structural Analysis Interview questions and answers are given just below to them. These sample Structural Analysis questions are framed by experts. who train for Learn Structural Analysis Online to give you an idea of Structural Analysis questions which may be asked in interview. We have taken full care to give correct answers for all the questions. Do comment your thoughts. Happy Job Hunting!
1. What is meant by Finite element method?
 Finite element method (FEM)is a numerical technique for solving boundary value problems in which a large domain is divided into smaller pieces or elements. The solution is determined by asuuming certain ploynomials. The small pieces are called finite element and the polynomials are called shape functions.

2. List out the advantages of FEM.
  •        Since the properties of each element are evaluated separately differnt material properties can be incorporated for each element.
  •        There is no restriction in the shape of the medium.
  •        Any type of boundary condition can be adopted.

3. List out the disadvantages of FEM.
  • The computational cost is high.
  • The solution is approximate and several checks are required.

Structural Analysis Interview Questions & Answers
4. Mention the various coordinates in FEM.
  •  Local or element coordinates
  •  Natural coodinates
  •  Simple natural coodinates
  •  Area coordiantesor Triangular coordiantes
  •  Generalised coordinates
5. What are the basic steps in FEM?
�       Discretization of the structure
�       Selection of suitable displacement fuction
�       Finding the element properties
�       Assembling the element properties
�       Applying the boundary conditions
�       Solving the system of equations
�       Computing additional results

6. What is meant by discretization?
Discretization is the process of subdividing the given body into a number of elements which results in a system of equivalent finite elements.

7. What are the factors governing the selection of finite elements?
=> The geometry of the body
=> The number of independent space coordinates
=> The nature of stress variation expected

8. Define displacement function.
Displcement function is defined as simple functions which are assumed to approximate the displacements for each element. They may assumed in the form of poynomials, or trignometrical functions.

9. Briefly explain a few terminology used in FEM.
The various terms used in FEM are explained below.
=>      Finite element-Small elements used for subdividing the given domain tobe  analysed are called finite elements. The seelements may be 1D, 2D or 3D elements depend in on the type of structure.
=>        Nodes and nodal points- The intersection of the differnt sides of elements are called nodes.

Nodes are of two types - external nodes and internal nodes.
O External nodes - The nodal point connecting adjacent elements.
O Internal nodes- The extra nodes used to increase the accuracy of solution.

=>          Nodal lines - The interface between elements are called nodal lines.
=>           Continuum- The domain in which matter exists at every point is called a continuum. It can be assumed as having infinite number of connected particles.
=>           Primary unknowns- The main unknowns involved in the formulation of the element properties are known as primary unknowns.
=>           Secondary unknowns- These unknowns are derived from primary unknowns are known as secondary unknowns. In displacement formulations, displacements are treated as primary unknowns and stress, strain, moments and shear force are treated as secondary unknowns.

10.            What are differnt types of elements used in FEM?
The various elements used in FEM are classified as:
=>       One dimensional elements(1D elements)
=>       Two dimensional elements(2D elements)
=>       Three dimensional elements(3D elements)

13.            What are 3-D elements? Give examples.
3-D elements are used for modeling solid bodies and the various 3-Delements are tetrahedron, hexa hedron, and curved rectangular solid.

14.            What are axisymmetric elements?
Axisymmetric elements are obtained by rotatinga1-D line about an axis. Axisymmetric elements are shown in the figure below.

15.            Define Shape function.
Shape function is also called an approximate function or an interpolation function whose value is equal to unity at the node considered and zeros at all other nodes. Shape function is represented by Ni where i =nodeno.

16.            What are the properties of shape functions?
The properties of shape functions are:
=>       Theno of shape functions will be equal to theno of nodes present in the element.
=>        Shape function will have a unit value at the node considered and zero value at other nodes.
=>       The sum of all the shape function is equal to 1. i. e. SNi =1

17.            Define aspect ratio.
Element aspect ratio is defined as the ratio of the largest dimension of the element to its smallest dimension.

18.            What are possible locations for nodes?
The possible locations for nodes are:
=>Point of application of concentrated load.
=>Location where there is a change in intensity of loads
=>Locations where there are discontinuities in the geometry of the structure
=>Interfaces between materials of different properties.

19.            What are the characteristics of displacement functions?
Displacement functions should have the following characteristics:
The displacement field should be continuous.
=>       The displacement function should be compatible between adjacent elements
=>       The displacement field must represent constant strain states of elements
=>        The displacement function must represent rigid body displacements of an element.

20.            What is meant by plane strain condition?
Plane strain is a state of strain in which normal strain and shear strain directed perpendicular to the plane of body is assumed to be zero.

=> Also Read 53 TOP Structural Analysis MCQs

Real Time Induction Motor Interview Questions And Answers

1. How does the Induction motor work? (OR) Why does the Rotor rotate?
When the 3 phase stator windings are fed by 3 phase supply, a magnetic flux of constant magnitude which is rotating at synchronous speed is set up.
The flux passes through the air-gap and sweeps past the rotor surface  thus it cuts the rotor conductors.
Due to the relative speed between the rotating flux and the stationary rotor conductors, an emf is induced in the stationary rotor conductors as per the Faraday's laws of electromagnetic induction.
The frequency of the induced emf is the same as the supply frequency.
Its magnitude is proportional to the relative velocity between the flux and the conductors.
Its direction will be as per Fleming's right hand rule.
Since the rotor conductors form a closed circuit the rotor current is produced.
This current's direction will oppose the very cause producing it ( as per Len's law)
Here the cause is the relative velocity between the rotating flux of the stator and the stationary rotor conductors.
Hence, in order to reduce the relative speed, the rotor begins to rotate in the same direction as that of the rotating magnetic flux and tries to catch up with the rotating flux. Thus the rotor of induction motor starts to rotate.

2. What is the general working principle of Induction motor?
The conversion of electrical power into mechanical power takes place in the rotating part of an electric motor.
In DC motors the electrical power is conducted directly to the armature through brushes and commutator.
Thus the DC motor can be called as conduction motor. But in case of AC motors, the rotor receives electric power, not by conduction but by induction.
This is exactly in the same way as the secondary of two winding transformer receives its power from the primary.
That is why such motors are known as induction motors.
Thus an induction motor is also known as rotating transformer ( ie, one in which primary winding is stationary and the secondary is free to rotate)

3. What is the advantage of skewed stator slots in the rotor of Induction motors?
In the induction motor design, the rotor slots are purposely made with a slight skew arrangement. It will not be parallel to the shaft.
This is for the purpose of reducing magnetic locking or reducing magnetic attraction between stator and rotor teeth.
In addition to that this arrangement will help to reduce the magnetic hum and noise.

4. What is meant by cogging in the Induction motor? How to prevent the cogging?
When the number of teeth in stator and rotor are equal, the stator and rotor teeth have a tendency to align themselves exactly opposite to each other, since this corresponds to minimum reluctance position. In such case the rotor may refuse to accelerate. This phenomenon is called as magnetic locking or cogging.
This problem can be prevented by proper choice of stator and rotor slots and also by skewing the rotor slots by one slot pitch.

5. What are the various methods of measuring slip?
1. By actual measurement of rotor speed
2. By measurement of rotor frequency
3. Stroboscopic method

6. What are the various methods of speed control in three phase induction motors?
(i) Control from stator side
1. By changing the supply frequency
2. By changing the number of stator poles
3. By changing the supply voltage
(ii) Control from rotor side
1. By inserting resistance in rotor circuit
2. By various ways of cascade connection
3. By injecting EMFs in the rotor circuit.

7. What is meant by crawing in the induction motor?
In induction motors, particularly squirrel cage type induction motors, sometimes exhibit a tendency to run stably at speeds as low as one-seventh of their synchronous speed Ns. This phenomenon is known as crawling of an induction motor and the speed is called as crawling speed.
Hiried Induction Motor Interview Questions And Answers

8. What is an Induction Motor?
An induction motor (IM) is a type of asynchronous AC motor where power is supplied to the rotating device by means of electromagnetic induction.

9. What is an Electric Motor?
An Electric Motor converts electrical power to mechanical power in its rotor.

10. How to supply power to rotor?
In a DC motor this power is supplied to the armature directly from a DC source, while in an AC motor this power is induced in the rotating device.

11. Why an Induction Motor sometimes called Rotating transformer?
An induction motor is sometimes called a rotating transformer because the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part) is the secondary side.

12. Who invented Induction Motor?
Nikola Tesla.

13. What is the basic difference between Synchronous motor and an Induction Motor?
The basic difference between an induction motor and a synchronous AC motor is that in the latter a current is supplied onto the rotor. This then creates a magnetic field which, through magnetic interaction, links to the rotating magnetic field in the stator which in turn causes the rotor to turn. It is called synchronous because at steady state the speed of the rotor is the same as the speed of the rotating magnetic field in the stator.

14. Why stator windings are arranged around the rotor?
the induction motor does not have any direct supply onto the rotor; instead, a secondary current is induced in the rotor. To achieve this, stator windings are arranged around the rotor so that when energised with a polyphase supply they create a rotating magnetic field pattern which sweeps past the rotor. This changing magnetic field pattern can induce currents in the rotor conductors. These currents interact with the rotating magnetic field created by the stator and the rotor will turn.

15. Why the speed of the physical rotor and the speed of the rotating magnetic field in the stator must be different?
the speed of the physical rotor and the speed of the rotating magnetic field in the stator must be different, or else the magnetic field will not be moving relative to the rotor conductors and no currents will be induced.

16. What is the SLIP?
This difference between the speed of the rotor and speed of the rotating magnetic field in the stator is called slip. It is unitless and is the ratio between the relative speed of the magnetic field as seen by the rotor to the speed of the rotating field. Due to this an induction motor is sometimes referred to as an asynchronous machine.

17. How many types of Induction Motor ?
Based on type of phase supply
Three phase induction motor (self starting in nature)
Single phase induction motor (not self starting)
Squirrel-cage induction motor
Slip ring induction motor

18. What is the relationship between the supply frequency number of poles and sycnchronous speed?
f = Pns/2

19. What is a Synchronous Speed?
\mbox{Synchronous speed, }n_s = \frac{120f}{P}\quad[\mbox{rev/min}]

20. What is a Rotor Speed?
Rotor speed, nr = ns(1-s)

21. How to calculate the Slip?
Slip is calculated using:

s = [ns-nr]/ns

22. What is a Stator?
The stator consists of wound 'poles' that carry the supply current that induces a magnetic field in the conductor. The number of 'poles' can vary between motor types but the poles are always in pairs (i.e. 2, 4, 6, etc.).

23. How many types of Rotor are there?
There are two types of rotors
Squirrel Cage rotor.
Slip Ring rotor.

24. What techniques is used to produce a desired Speed?
The most commonly used technique is Pulse Width Modulation in which a DC signal is switched on and off very rapidly, producing a sequence of electrical pulses to the inductor windings.

25. What is the difference between DC motors and the Induction motors?
The induction motor has no brushes and is easy to control, many older DC motors are being replaced with induction motors and accompanying inverters in industrial applications.

26. How an Induction Motor is started? Why the Starter is Used?
When the motor is started, the slip is equal to 1 as the rotor speed is zero, so the induced emf in the rotor is large. As a result, a very high current flows through the rotor. This is similar to a transformer with the secondary coil short circuited, which causes the primary coil to draw a high current from the mains. Similarly, when an induction motor starts, a very high current is drawn by the stator, on the order of 5 to 9 times the full load current. This high current can damage the motor windings and because it causes heavy line voltage drop, other appliances connected to the same line may be affected by the voltage fluctuation. To avoid such effects, the starting current should be limited. A soft start starter is a device which limits the starting current by providing reduced voltage to the motor. Once the rotor speed increases, the full rated voltage is given to it.

27. What is a Rotor?
The rotor is the non-stationary part of a rotary electric motor or alternator, which rotates because the wires and magnetic field of the motor are arranged so that a torque is developed about the rotor's axis. In some designs, the rotor can act to serve as the motor's armature, across which the input voltage is supplied. The stationary part of an electric motor is the stator. A common problem is called cogging torque.

28. What is a Stator?
The stator is the stationary part of an electric generator or electric motor. The non-stationary part on an electric motor is the rotor.
Depending on the configuration of a spinning electromotive device the stator may act as the field magnet, interacting with the armature to create motion, or it may act as the armature, receiving its influence from moving field coils on the rotor.

29. What is Commutator?
A commutator is an electrical switch that periodically reverses the current direction in an electric motor or electrical generator. A commutator is a common feature of direct current rotating machines. By reversing the current direction in the moving coil of a motor's armature, a steady rotating force (torque) is produced. Similarly, in a generator, reversing of the coil's connection to the external circuit produces unidirectional current in the circuit. The first commutator-type direct current machine was built by Hippolyte Pixii in 1832,

30. What is an Armature?
An armature is one of the two principal electrical components of an electromechanical machine--a motor or generator. The other is the field winding, field magnet. The role of the "field" component is simply to create a magnetic field (magnetic flux) for the armature to interact with, so this component can comprise either permanent magnets, or electromagnets formed by a conducting coil. The armature, in contrast, must carry current so it is always a conductor or a conductive coil, oriented normal to both the field and to the direction of motion, torque (rotating machine), or force (linear machine). The armature's role is two-fold: (a) to carry current crossing the field, thus creating shaft torque (in a rotating machine) or force (in a linear machine), and (b) to generate an electromotive force ("EMF").

31. What is a Cogging Torque?
Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets of the rotor and the stator slots of a Permanent Magnet (PM) machine. Also termed as detent or 'no-current' torque, it is an undesirable component for the operation of such a motor. It is especially prominent at lower speeds, with the symptom of jerkiness.

32. What are the advantages and disadvantages of Induction Motors?
It is simple and rugged in construction
It is relatively cheap
Induction motors require less maintenance
Induction motor has high efficiency and reasonably good power factor
3-phase induction machines are self starting

Induction motors are essentially a constant speed motor and its speed cannot be changed easily
Its starting torque is inferior to dc shunt motor

bStarting torque will be maximum when the rotor resistance / phase is equal to standstill rotor reactance / phase

34. Slip ring induction motor advantages and disadvantages compared to squirrel cage motors?
High starting torque with low starting current
Smooth acceleration under heavy loads
No abnormal heating during starting
Good running characteristics after external rotor resistances are cut out
Adjustable speed
The initial and maintenance costs are greater than those of squirrel cage motors
The speed regulation is poor when run with resistance in the rotor circuit

35. Methods to control speed of Wound Rotor Motors?
Answer: The speed of wound rotor motors are changed by changing the slip of the motor. This can be achieved by:
Varying the stator line voltage
Varying the resistance in the rotor circuit
Inserting and varying a foreign voltage source in the rotor circuit

36. Explain how Torque-Slip Characteristics vary when adding resistance to rotor circuit?
Answer: The addition of resistance to the rotor circuit does not change the value of maximum torque but it only changes the value of the slip at which the maximum torque occurs

37. Disadvantages of Star-Delta Starting of Induction motor?
Answer: In Star-Delta starting induction motor stator is connected in star connection for starting after picking up speed it is connected to delta connection. When induction motor is connected in star connection stator phase voltage reduced by 1/(31/2 ) times the line voltage. This also results in reduced starting torque (1/3 times compared to delta connection).

Latest Induction Motor Interview Questions for freshers and Experienced pdf

Recently Asked Electrostatics Interview Questions And Answers

1. Explain The Concept Of Density ?
One of the properties characteristic of every material is its density. We observe that a small piece of one material may be heavier than a much large piece of another material. The mass per unit volume of a substance is called its density
p = m/V
Units of density are determined by dividing the chosen unit of mass by the unit of volume, as kilogram per cubic meter, gram per cubic centimeter, or slug per cubic foot.

It is sometimes helpful to use another quantity called weight-density, or weight per unit volume:                                  
D = W/V

Since W = mg, we have a simple relation between density and weight-density:
D = ?g

Weight-density is commonly used when we are concerned with effects depending upon force, while density is used when mass is to be considered.

Solids and liquids are only slightly compresses by even large stresses; hence their densities are almost constant under usual conditions. Gases are readily compressed; hence it is necessary to states the conditions under which the densities are measured.

2. Enlighten The Phenomenon Of Electromotive Force ?
In order to maintain an electric current, some agency is required to expend energy in moving the charge around a circuit. With the exception of a few metals near absolute zero, the superconductors, all conductors present some opposition to the flow of charge so that work must be done to maintain a current. An agency capable of causing such a flow by converting other forms of energy to electrical work is called a seat of electromotive force or a source of current.

It should be clearly understood that a source of current does not manufacture charge but merely moves the charge through a circuit. In most circuits this agency is concentrated in one or a few parts of this agency is concentrated in one or a few pats of the circuit. The source must create an electric field in all parts of the circuit to cause the charges to move against the various opposing effects they may encounter.

The electromotive force, or emf, of a source is the energy per unit charge transformed in a reversible process. (The term “electromotive force” is an old term now rooted in the language of physics; its choice was unfortunate, as this quaintly is not a force. Hence its abbreviation emf will be used hereafter.) In the mks system, emf will be used hereafter).

An emf causes difference of potential to exist between points in the circuit. Thus there is an intimate relation between emf and potential difference. An emf associated only with reversible conversions of energy, whereas potential difference exists not only in source of emf but also in resistors, which convert energy to heat irreversibly. The distinction is sometimes useful and will becomes clearer as we proceed.

In the simple circuit charge flow through the circuit, the cell converts chemical energy to electrical energy, giving rise to an emf. The lamp is a resistive conductor called a resistor; it converts electric energy to heat, and work done on the charge by the electric field, as the charge moves through the resistor, is evidenced by the presence of a potential difference between the ends of the resistor. A small amount of the total electric energy converted from chemical energy in the cell also produces heat inside the cell.
Electric circuits are conventionally reprinted by circuit diagrams employing standard symbols.

3. Describe Electrostatics In Nature Lightning ?
Man has always been curious about and often awed by the power of lightning> Benjamin Franklin’s experiment approximately 200 years ago with a kite in which showed that lightning consisted of the same type of electricity that could be produced on earth by electrostatic means is possibly the most famous study made of lightning . Although this phenomenon has been the topic of considerable research, scientists have failed to agree upon the cause and the nature of lightning.
We know that lightning is a violent example of the tremendous electrostatic charges that can occur in nature, but there are several different explanations given about the manner in which the charges that cause lightning are produced in a cold. Most of these theories are built upon the premise that because of violent air currents in cloud, and the interaction of ions and water droplets and ice [articles, positive negative charges are produced in a cloud and are then separated with the positive charges moving upward and the negative charges moving downward.
To understand this generalization, let us first look at the makeup of a thunderhead clod. In the “mature” stage the cloud top will reach up to 10,000 to 15,000 m (40,000ft) where the temperature is about -50°C. within this cloud, which may have its lower layer at a height of 5,000 ft and a temperature of around +20°C, there are strong updrafts reaching a speed of 60 mi/h. the water vapor in the cooled below its freezing immediately until it has a “seed,” or nucleus, to form upon, and as a result it becomes super cooled.
However, once ice starts to form, with crystals grow rapidly and fall through the rising air causing a down draft of cold air. When this cold air reaches the bottom of cold air. Reaches to the ground just ahead of the rain, causing the sometimes noticed chill that rain, causing the sometimes noticed chill that precedes a rainstorm.
Let us consider the most popular theory that the lighter “spray like” parts of the torn off darning falling becomes positively charged and are then carried upward into the cold upper layer of the cloud. The heavier particles become negatively charged and continue to move downward and in so doing acquire more negativity as they grow in size.

4. Describe The Emf Induced By Motion ?
Whenever a change q moves in a magnetic field, the charge experiences a force F the magnitude of which given by
F = quB sin? = q/t  lB sin?

In vector form the force is given by
F = qv × B = q/t l × B

The force on the charge +q is at right angles to v and B. in the example illustrated in the force on a positive charge would be upward. A moving charge constitutes a current. The force on a charge in motion is that on the equivalent conventional current.  The vectors representingv, B and F are mutually perpendicular. If the charge is free to respond to this force, it will move in the direction of F.

An electric conductor, such as a copper wire, has free electrons in it. Consider a wire moving across a magnetic field. The component B sin ? perpendicular to the velocity will exert a force on charge in the wire along the direction of the wire. Positive charges in the wire would experience a force directed toward b; electrons experience a force in the opposite direction, and the free electrons accumulate at a leaving a deficiency of electrons at b.

Equation gives F/q = vB sin ?. Thus an electric field is set up in the conductor directed from a towards b, with a magnitude E = F/q = vB sin?. The emf e induced in the wire of length l is                      
e = W/q = Fl/q = Eql/q = lvB sin ?

When B is expressed in webers per square meter, l in meters, and v in meters per second, the emf is in joules per coulomb, or volts.

The emf exists whether or not there is a complete circuit for current. If the moving conductor slides along stationary conducting rails a current will be establishes in the sense shown.

5. Express Faraday Law Of Electrolysis ?
Quantitative measurements made by Faraday (1833) contributed to the understanding of the process occurring in electrolytic cells and showed a stinking relation between the electrolytic behavior and the chemical properties of various substance. Faraday established by experiment the following two laws of electrolysis:

First law: The mass of substance separated in electrolysis is proportional to the quantity of in electrolysis is proportional to the quantity of electricity that passes.

Second law: The mass of substance deposited is electrolysis is proportional to the quantity of electricity that passes.

Faraday’s law may be expressed by the following symbolic statements:

m ? Q          (Q = It)        
m ? c          (c = (atomic mass)/(valence ))
m = kcQ = zQ = zIt         (z = kc)

Where k is a proportionality constant, whose value depends only upon the units involved, mis the mass deposited, and z is a constant for a given substance (but different for different substance), which is known as the electrochemical equivalent of the substance under consideration. The electrochemical equivalent of a substance is the mass deposited per unit charge. In the mks system it numerically the number of kilograms deposited in one second by an unvarying current of one ampere.

6. Express The Relation Between Forced Vibration And Resonance ?
Wherever a vibrating body is coupled to a second body in such a manner that energy can be transferred, the second body is made to vibrate with a frequency equal to that of the original vibrator. Such a vibration is called a forced vibration. If the base of vibrating turning fork is set against a tabletop, the tabletop is forced to vibrate. This combination radiates energy faster than the fork could alone. Similarly, a vibrating string is inefficient in transferring energy to surrounding air unless it is coupled to some sounding board.

Whenever the coupled body has a natural frequency of vibration equal to that of the sources, there is a condition of resonance. Under this condition the vibrator releases more energy per unit time, and the sound is greatly reinforced. Hence the external power supplied to a resounding system must be increased; otherwise its vibrations will be quickly damped.

The reinforcement of sound by resonance with its accompanying release of large amounts of energy has many useful and many obnoxious consequences. The resonance of the many obnoxious consequences.  The resonance of the air column in an organ pipe amplifies the otherwise almost inaudible sound of the vibrating airjet. Resonance would produce objectionable distortions of speech or music.
Hiried Electrostatics Interview Questions With Answers
7. How Number Of Lines Of Force Through A Surface Can Be Expressed ?
An advantage of this law is the fact that the net number of lines of force through a surface can be expressed in terms of the electric field intensity at that surface. An alternative use of this law is the computation of the electric field intensity produced by symmetrical charge distribution in terms of the electric flux produced by these charges.

8. Express The Relation Between Number Of Lines Of Force And The Net Positive Charge ?
A signification relation between the net numbers of lines of force passing through any closed surface in the outward direction and the net positive charge enclosed within that surface was discord charged enclosed within that surface was discovered by Karl Friedrich Gauss (1777-1855). In the preceding sections it was shown (for the case of an isolated point charge) that the total number of lines of electric flux emerging from a charge is exactly equal to that charge (in the mks system of units). It is evident that the same net number of lines of force will pass out of any closed surface of any shape if the surface completely encloses the charge the generalization of this conclusion is known as Gauss’ law.

The net number of lines of force in an electric field that cross any closed surface in an outward direction is equal (in the msk system) to the net positive charge enclosed within that surface.

In symbols Gauss’ law may be stated by the equation previously given as ? = ?Q.

9. Describe Induced Emf And Currents ?
Consider coil of wire connected to a sensitive galvanometer G. if the N pole of a bar magnet is thrust into the coil, the galvanometer will deflect, indicating a momentary current in the coil in the direction specified by the arrows. This current in called an induced current and the process of generating the emf is known as electromagnetic induction. As long as the bar magnet remains at rest within the coil, no current in induced. If, however, the magnet is quickly removed from the coil, the galvanometer will indicated a current in the direction. Opposite that at emf is induced when there is any change of magnetic flux linked by the conductor.

An emf may also be induced in a coil by the change in the magnetic field associated with a change in current in a nearby circuit. For example, a coil M connected to a battery through switch S. A second coil N connected to a galvanometer is nearby. When the switch S is closed, producing a current in the coil M in the direction shown, a momentary current is induced in coil N in a direction (arrow a) opposite to that in M. if S is now opened, a momentary current will appear in N, having the direction of arrow b. in each case there is a current in N only while the current is M is changing. A steady currents in M accompanied by a motion of M relative to N is also found to induce a current in N. we observed that, in all cases in which a currents is induced in N, the magnetic flux through N is also changing.

10. State Lenz Law Of Induced Emf ?
Lenz’s law states that, whenever an emf is induced, the induced current is in such a direction as to oppose (by its magnetic action) the change inducing the current.

Lenz’s law is a particular example of the principle of conservation of energy. An induced current can be produced heat to do chemical or mechanical work. The work energy must come from the work done to the motion of a magnet or a coil, work is done; therefore the motion must be resisted by a force. This opposing force comes from the action of the magnetic field of the induced current. When a change in current in a primary coil induces an emf in a neighboring secondary coil, the current in the secondary will be in such a direction as to require the expenditure of additional energy in the primary to maintain the current.    

11. Describe The Various Systems Of Units In Electrostatics ?
Two families of units are useful in the areas of electrostatics: the mks system and the system of cgs electrostatic units (esu). The electrostatic units will first be considered because of their historical significance and their simplicity.

If can be seen that there are two new concepts to be defined that have not previously been considered, namely, those represented by the electrostatic system to selected the concept represented by the symbols k and Q. it is most convenient in the electrostatic system to selected the concept represented by k as the one to be arbitrarily designated as fundamental (like length, mass, and time in mechanics). Then Q can be defined from Coulomb’s law. From this agreement, k is arbitrarily assigned the value of exactly. I dyn cm2 per unit charge2 for empty space. The esu of charge, usually called the statcoulomb (statiC), is defined as a point charge of such a magnitude that it is repelled by a force of one dyne if it is placed one centimeter away from an equal charge in empty space. The size of the statcoulomb makes it convenient for many problems in electrostatics.

12. Determine The Construction Of Ac Generator ?
The simplest possible generator is a single coil of wire rotating in a uniform magnetic field. The emf induced in such a case is an alternating emf, and hence such a generator is referred to as and hence such a generator is referred to as an ac generator. The coil in which the emf is induced is called the armature.

A high voltage may be obtained in an ac generator by having the coil wound on an iron core, the flux linked by the coil being thus increased, and also by having a large number of turns in series for each coil. Where the coil rotates, the ends of the coils are connected to circular ring called collecting rings or slip rings. Carbon (graphite) brushes bearing on these rings make connection to the outside circuit. The basic elements of an ac generator are (1) a field magnet, (2) the armature genitors the armature is made stationary and the field magnet is caused to rotate.

13. State Faraday Ice Pail Experiments ?
Several significant experiments, originally performed by Faraday with a metallic ice pail and an electroscope, are useful in illustrating some of the facts stated above. The pail is connected to the electroscope by a conducting wire.

When a charged ball, held by an insulating thread, is lowered into the pail, the leaves of the electroscope diverge, showing that they possess an induced charge. No charge in the divergence of the leaves is noticed when the charged ball is moved to various places inside the pail. This shown that the number of induced charges inside the pail is just equal to the charge on the ball. Now, if the ball is touched to a wall of the pail, no charge in the divergence of the leaves is observed. The ball is found to have lost its charge and the outside of the pail and the electroscope has gained the charge lost by the ball. When the ball touches the wall, its charge just neutralizes the charges of opposite sign that were on the inside of the pail.

If the ball is again similarly charged and reintroduced into the pail and touched to the pail, it will be found that the pail acquires an additional charge, equal in magnitude and sign to the original charge. This procedure can be continued until the pail is charged to a very high potential.

14. Consider The Thermoelectric Effects Of Current ?
In considering thermoelectric effects, we have to realize that we are dealing with a non-equilibrium situation. A general theory of non-equilibrium is beyond our means, suffice it to say that Lars Onsager, with a paper entitled” reciprocal relations in irreversible processes” induced some fundamental insights as late as 1930; he received the Nobel Prize for his contribution to non-equilibrium thermodynamics in 1968-for chemistry, of all things. However, what we should aware of, is the essential statement of non-equilibrium theory:

As long as there is no equilibrium, we always have currents of something trying to establish equilibrium by reducing a gradient in something else that is the actual cause of the non-equilibrium. A gradient in the electrical potential, e.g., cause out well-known electrical currents, and a gradient in a concentration causes diffusion currents.
But we must abstract even more, and consider things like entropy currents as well as all kinds of combinations of gradients and currents
While Onsager discovered some quite general relations between gradients and currents, we will not delve into details here, but only look a bit more closely at what causes some thermoelectric effects of current.

15. Describe Seebeck Thermoelectric Effect Of Current ?
See beck in 1821 found that if two wires of different metals say copper and iron are joined at their ends A and B through a low resistance galvanometer G to from a closed circuit and if one of the junctions say A is heated and the other junction B is kept cold the galvanometer shows a deflection this must be due to a current in the circuit called thermo eclectic current the current must further be due to certain called thermo the assembly of two different metals joined at their ends to have two junctions in a circuit is called a thermocouple. This phenomenon of thermo-electricity was discovered first of all by see beck. Hence it is also called see beck effect.

Thus see beck effect is the phenomenon of generation of an electric current in a thermocouple by keeping its two junctions at different temperatures.

The direction of current in Cu – Fe thermocouple is from Cu to Fe through hot junction and can be remembered by the world chl. In Sb-Bi thermocouple the direction of current is Sb to Bi through cold junction it can be recollected by ABC.

See beck found that the magnitude and direction of thermo developed in a thermo couple depends up.

The nature of metals forming the thermo couple.
Difference in temperatures of the two junctions.
The see beck effect is reversible. It means if the hot and the cold junctions are interchanged. The direction of thermoelectric current is reversed. Thus see beck effect is a reversible effect.

See beck from his experimental investigations arranged a number of metals in a series know as see beck series. Some of the metals of this series in the order see beck arranged them are given below.

Bi, Ni, Co Pd, Pt, Cu, Mn, Hg, Pb, Sn, Au, Ag, Zn, Cd, Fe, Sb, Te,.

When any two of these metals from a thermocouple current flows through the hot junction from a metal occurring earlier, to a metal occurring later, in the series.

See beck also found that for a given difference of temperatures of two junctions the larger is the gap in see beck series between the metals forming the thermo couple the greater will be the thermo emf. Generated. That is why thermo emf developed is maximum in a thermo couple of antimony and bismuth for a given difference in temperatures of the two junctions. The thermo emf is of the order of 10-3 V or less.

For a temperature difference of 100C between the two junctions the thermo produced in Cu-Fe. Thermocouple is only 0.0013V and in Sb-Bi thermocouple is 0.008V.

16. Describe The Origin Of Thermo ?
When two different metals are brought into contact, at the junction the free electrons tend to diffuse from the metal swath greater free electron density to the other with lower free electron density due to this diffusions a potential different is developed at the junction of the two metals called contact potential when booth the junctions are at the same temperature the contact potentials at the two junctions will be the same.

Hence no current flows in the thermocouple. But if one junction id heated up the rate of diffusion of free electrons at that junction will charge. As a result of it’s the contact potentials at the two junctions will become different and there will be an effective potential difference in the circuit called thermo.

Thus the term produced in a thermocouple is equal to the difference in contact potentials at the two junctions A and B and is given by V AB = V A – V B

17. Describe The Construction And Working Of Thermoelectric Thermometers ?
A thermoelectric thermometer is used for the measurement of temperatures both low and high.
Principle: Its working is based on see beck effect thermocouples of different metals are constructed depending upon the temperature to be measured.
Construction: The wires forming the thermocouple are welded together at one end and this end forms the hot junction. The portions of the wires near the hot junction are properly insulated from each other by enclosing them in a hard-glass capillary tube C.T. the wires are passed through mice discs D, which are fitted one above the other in a porcelain tube T. the ends of these wires are connected to the terminals T1 and T2 to these terminals are connected compensating leads L1 and L2 of the same materials as those forming the thermocouple itself. By so doing the cold junction is shifted to a convenient place where a constant temperature of OC is maintained.

By keeping hot junction at different known temperatures the corresponding values of thermo are noted using distal voltmeter in the circuit of thermocouple. The digital voltmeter gives its internal resistance is very high (about 10 ?). A graph plotted between the temperature of hot junction and Themo the curve so obtained is called calibration curve.

To find the unknown temperature of a given bath the hot junction is placed in the given bath. The thermo so generated is measured. The temperature corresponding to this value of thermo is determined from the calibrations curve.

Note it is important to note that thermocouple should not be used to measure the temperature above the neutral temperature.

18. Describe The Advantages Of Thermoelectric Thermometers ?
Thermoelectric thermometers can be used over much wide3er range of temperatures; ranging from – 200C to 1600C.
These thermometers are cheap and can be constructed easily.
These can be used to measure the temperature of small cavity.
Their thermal capacity being low they attain the temperature to be measured very quickly and are thus useful for measuring changing temperatures.

19. What Are The Disadvantages Of Thermoelectric Thermometers ?
Since these thermometers are not direct riding thermometers so they cannot be used for calorimetric purposes.
There is no common relation connecting thermo and the temperature of a junction in any thermocouple. Therefore the given thermo couple has to be calibrated first.
For the measurement of temperature over different ranges, different thermocouples are to be used.

20. Define Thermoelectric Power ?
Thermo electric power is defined as the rater of charge of thermo with temperature it is also called see beck coefficient and is denoted by S.
From experimental study it was concluded that the variation of thermo e with the temperature C of the hot junction when cold junction is at OC is a parabolic curve represented by the equation
E = a ? + 1 / 2 ß ?2

Where a and ß are constants which depend upon the nature of the metals forming the thermocouple and the temperature difference of the two junction.

The thermoelectric power (called see beck coefficient) is given by

S = dE/d ? = ? + ß ?
It means S ? ?

21. Describe The Construction Of A Thermopile ?
A thermopile is a sensitive instrument used for detection of heat radiation and measurement of their intensity. It is based upon see beck effect.
A thermopile consists of a number of thermocouples of Sb –Bi all connected in series. One set of junctions on one side is coated with lamp black. The other set of junctions on the other side is well polished. The arrangement is enclosed in a funnel or horn shaped vassal. The two ends T1 and T2 of the thermopile are connected to a sensitive galvanometer.

Heat radiations coming from the funnel shaped side of the vessel are made to fall on the set of junctions coated with lampblack. These are absorbed and consequently the temperature of all the junctions in this set is raised. The other set of junctions being polished reflect these radiations and remain cold. Thermo is developed in each thermocouple. As thermocouples are connected in series, the thermoelectric current in each flow is in the same junction. The total current is therefore large and produces deflection in the galvanometer.

The deflection in the galvanometer indicates the existences of heat radiations. The deflection is calibrated to measure directly the intensity of heat radiations. This instrument is so sensitive that it can detect heat radiations from match stick lighted at a distance of 50 meters from the thermopile.

22. Describe The Working Of A Thermoelectric Refrigerator ?
The working of thermo-electric refrigerator is based on pettier effect. According to pettier effect, if current is passed through a thermocouple heat is absorbed at one junction and evolved at the other junction of the thermocouple. If on the whole the heat is a boarded, the thermocouple acts as thermoelectric refrigerator. Such a refrigerator has no muter or compressor. Its efficiently is small in comparison to congenital refrigerator. Thermo electric refrigerator is very useful when the region to be cooled is very small and the noise is not acceptable.

The thermocouple selected for the use of thermoelectric refrigerator should have the following characteristics.

Low resistivity so that the loss of energy in the form of joule heat is minimum.
Low thermal conductivity it will help in maintaining large temperature difference between the two junctions.
High thermo electric power.

23. What Is A Thermoelectric Generator ?
Thermocouple can be used to generate electric power using seek beck effect in remote areas. It can be achieved by heating one junction in a flame of kerosene oil lamp and keeping the other junction at room or atmospheric temperature. The thermo so developed is used to operate radio receivers or even radio transmitters.

24. Describe Thomson Effect Of Evolution Of Heat ?
Thomson’s effect was discovered by Thomson (later called Kelvin). According to this effect, if two parts of a single conductor are maintained at different temperatures, an e.m.f. is developed between them. The e.m.f. so produced is called Thomson’s e.m.f. If the steady current is passed through an unequally heated conductor, an absorption or evolution of heat in excess of Joule’s heat, takes place in the conductor.

Thus Thomson’s effect is the absorption or evolution of heat in excess of Joule heat when current is passed through an unequally heated conductor. Thomson effect is reversible effect.

To understand Thomson’s effect, consider an unequally heated rod AB of copper. Let the end A of the be at higher temperature than its end B. on passing the current from A to B in the rod, heat is evolved along the length of the rod. In case, the current is passed in the rod from end B to A, the heat is absorbed along the length of the rod. It is accounted due to the fact that in case of copper, the hot end of the rod is at higher potential and its cold end is at lower potential.

When current flows from hot end to cold end of copper rod i.e. from higher potential to lower potential, the energy is produced which is radiated out in the form of heat. When current is flowing from cold end to hot end of the copper rod i.e. from lower potential to higher potential, the energy required which accounts for the absorption of heat energy. Thomson’s effect for copper is positive. Other substances showing positive Thomson’s effect are Sb, Ag, Zn etc.

There are some other substances like Fe, Co, Bi, Pt etc. for which Thomson’s effect is negative. It means for such metals, Thomson’s effect is just reverse as that for copper. It means, according to Thomson’s effect for iron rod, heat is absorbed when current is passed from hot end to cold end and heat is evolved when current is passed from cold end to hot end of the rod.

For lead, Thomson’s effect is nil. It means no heat is evolved or absorbed when current is passed through an unequally heated rod of lead. It is due this reason that lead is used as a reference metal in thermoelectricity.

25. Explain Area Vector ?
Area is a scalar quantity. But in some of the problems it is convenient to treat it a a vector. The question is how to associate a vector to the area of a curved surface. Let us divide the given closed area into a large number of very small area elements. Each small area element may be treated as planar. As normal to the plane specifies the orientation of the place, therefore, the direction of a planar area vector is along its normal. But a normal can point in two directions, inwards or outwards. By convention the vector associated with every area element of a closed surface is taken to be in the direction of the outward normal.

Thus, an area element vector S at a point on a closed surface can be written as

?  =  (? )

where S in magnitude of the area element and  is a unit vector in the direction of outward normal at that point.

26. How Does Electric Flux Represent The Field Lines ?
Electric flux over an area in an electric field represents the total number of field lines crossing this area.

We know that the number of field lines crossing a unit area placed normal to the field at a point is a measure of strength of electric field E at that point. If we place a small planar element of area ?S normal to E at this point, number of electric filed lines crossing this area element is proportional to E (?S) note that it is not proper to say that number of field lines crossing the area is equal to E (?S). The number of field lines is after all a matter of how many field lines we choose to draw. What is physically significant is the relative number of field lines crossing a given area at different points.

If we tilt the area element by angle ? [or we tilt E w. area element by angle ?, the number of field lines crossing the area will be smaller. As projection of area element normal to E is ?S cos ? (or component of E normal of electric filed lines crossing area ?S is proportional to E?S cos ?.

27. Describe The Relation Between Electric Intensity And Electric Potential ?
To obtain relation between electric intensity E and electric potential V, let us consider two equipotential surfaces A and B spaced closely as shown in fig. 1 (c) let the potential of A be VA = V and potential of B be VB = (V + dV) where dV is increase in potential in the direction of electric intensity E normal to A and B.

Suppose dr is perpendicular distance between the two equipotential surfaces. When a unit positive charge is taken along this perpendicular distance from the surface B to the surface A against the electric field.

Work done WBA = | E | dr

By definition

WBA = VA – VB = V – (V + dV) = - dV
 |E| dr = – dV

28. Describe The Electrostatic Potential Energy Of A Charge In An Electrostatic Field ?
Like the potential energy of a mass in a gravitational field we can define electrostatic potential energy of a charge in an electrostatic field.
For the sake of simplicity, let us assume that electrostatic field  is due to charge + Q placed at the origin. Let a small test charge + q be brought from a point A to a point B, against the repulsive force on it due to charge + Q we shall assume that the test charge +q is so small that it does not disturb the original configuration of charge + q at the origin further we assume that an external force   ext applied is just sufficient to counter the repulsive electric force  on the test charge q so that net force on test charge q is zero and it maces from A to B without any acceleration.

In this situation, work done by external force is evasive of work done by the electric force and gets fully stored in the charge q in the form of its potential energy.

On reaching B, if the external force applied on q were removed, the electric force will take the test charge + q away from source charge + Q. the strode potential energy at B is used to provide kinetic energy to the charge q in such a way that the sum of kinetic and potential energies at every point is conserved.

29. What Does Electrostatic Potential Of A Body Represents?
Basically electrostatic potential of a body represents the degree of electrification of the body it determines the direction o flow of charge between two charged bodies placed in contact with each other. The charge always flows from a body at higher potential to another body at lower potential the flow of charge stops as soon as the potentials of the two bodies become equal.

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