Top 30 Electrical interview question and answer

Question 1. What Is The Difference Between A Verilog Task And A Verilog Function?

Answer: The following rules distinguish tasks from functions:
A function shall execute in one simulation time unit; a task can contain time-controlling statements.
A function cannot enable a task; a task can enable other tasks or functions.
A function shall have at least one input type argument and shall not have an output or input type argument; a task can have zero or more arguments of any type.
A function shall return a single value; a task shall not return a value.

Question 2. Explain The Differences Between "direct Mapped", "fully Associative", And "set Associative" Caches

Answer: If each block has only one place it can appear in the cache, the cache is said to be direct mapped. The mapping is usually (block-frame address) modulo (number of blocks in cache).
If a block can be placed anywhere in the cache, the cache is said to be fully associative.
If a block can be placed in a restricted set of places in the cache, the cache is said to be set associative. A set is a group of two or more blocks in the cache. A block is first mapped onto a set, and then the block can be placed anywhere within the set. The set is usually chosen by bit selection; that is, (block-frame address) modulo (number of sets in cache). If there are n blocks in a set, the cache placement is called n-way set associative.

Question 3. What Is Electric Traction?

Answer: Electric traction means using the electric power for traction system (i.e. for railways,trams, trolleys etc).
Electric traction means use of the electricity for railways, trams, trolleys etc. Now a days, magnetic traction is also used for bullet trains. and basically, dc motors are used for electric traction systems.

Question 4. How Can You Start­up The 40w Tube Lite With 230v Ac/dc Without Using Any Choke/coil?

Answer: It’s possible by means of Electronic chokes, otherwise it’s not possible to ionize the particles in tube light with normal voltage.

Question 5. What Is “pu” In Electrical Engineering?

Answer: Pu stands for per unit and this will be used in single line diagram of power distribution and it is like a huge electrical circuit with no of components (generators, transformers, loads) with different ratings (in MVA and KV). To bring all the ratings into the common platform we use (pu) concept in which, in general, largest MVA and KV ratings of the component is considered as base values, then all other component ratings will get back into this basis. Those values are called as (pu) values.

Question 6. Operation Carried Out In Thermal Power Stations?

Answer: The water is obtained in the boiler and the coal is burnt so that steam is obtained this steam is allowed to hit the turbine, the turbine which is coupled with the generator generates the electricity.

Question 7. Why Link Is Provided In Neutral Of An Ac Circuit And Fuse In Phase Of Ac Circuit?

Answer: Link is provided at a Neutral common point in the circuit from which various connection are taken for the individual control circuit and so it is given in a link form to withstand high Amps. But in the case of Fuse in the Phase of AC circuit, it is designed such that the fuse rating is calculated for the particular circuit (i.e load) only. So if any malfunction happens the fuse connected in the particular control circuit alone will blow off.

Question 8. How Tube Light Circuit Is Connected And How It Works?

Answer: A choke is connected in one end of the tube light and a starter is in series with the circuit. When supply is provided, the starter will interrupt the supply cycle of AC. Due to the sudden change of supply, the chock will generate around 1000volts. This volt will capable of to break the electrons inside the tube to make electron flow. once the current passes through the tube the starter circuit will be out of the part. now there is no change of supply causes choke voltage normalized and act as minimize the current.

Question 9. What Is Marx Circuit?

Answer: It is used with generators for charging a number of a capacitor in parallel and discharging them in series. It is used when the voltage required for testing is higher than the available

Question 10. What Is Encoder, How It Function?

Answer: An encoder is a device used to change a signal (such as a bitstream) or data into a code. The code may serve any of a number of purposes such as compressing information for transmission or storage, encrypting or adding redundancies to the input code, or translating from one code to another.

This is usually done by means of a programmed algorithm, especially if any part is digital, while most analog encoding is done with analog circuitry.

Question 11. What Are The Advantages Of Speed Control Using Thyristor?

Answer: Advantages :

1. Fast Switching Characteristics than Mosfet, BJT, IGBT.
2. Low cost.
3. Higher Accurate.

Question 12. Why Human Body Feel Electric Shock ?? N In An electric Train During Running, We Did Nt Feel Any shock? Why?

Answer :Unfortunately our body is a pretty good conductor of electricity, The golden rule is Current takes the lowest resistant path if you have insulation to our feet as the circuit is not complete (wearing rubber footwear which doing some repairs is advisable as our footwear is a high resistance path not much current flows through our body).The electric train is well insulated from its electrical system.

Question 13. What Is The Principle Of Motor?

Answer: Whenever a current carrying conductor is placed in a magnetic field it produces turning or twisting movement is called as torque.

Question 14. Why, When Birds Sit On Transmission Lines Or Current Wires Doesn’t Get Shocked?

Answer: It is true that if birds touch the single one line (phase or neutral) they don’t get electrical shock… if birds touch 2 lines than the circuit is closed and they get electrical shock.. so if a human touch single one line(phase) then he doesn’t get shocked if he is in the air (not touching – standing on the ground if he is standing on the ground then touching the line (phase) he will get a shock because the ground on what we standing is like line (ground bed – like neutral)? and in most of the electric lines the neutral is grounded..so that means that human who touches the line closes the circuit between phase and neutral.

Question 15. What Is Meant By Armature Reaction?

Answer: The effect of armature flu to main flux is called armature reaction. The armature flux may support main flux or opposes main flux.

Question 16. What Happen If We Give 220 Volts Dc Supply To D Bulb R Tube Light?

Answer: Bulbs [devices] for AC is designed to operate such that it offers a high impedance to AC supply. Normally they have low resistance. When DC supply is applied, due to low resistance, the current through lamp would be so high that it may damage the bulb element.

Question 17. Which Motor Has High Starting Torque And Staring Current Dc Motor, Induction Motor Or Synchronous Motor?

Answer: DC Series motor has high starting torque. We can not start the Induction motor and Synchronous motors on load, but can not start the DC series motor without a load.

Question 18. What Is Acsr Cable And Where We Use It?

Answer: ACSR means Aluminium conductor steel reinforced, this conductor is used in transmission & distribution.

Question 19. What Is Vaccum Circuit Breaker? define With Cause And Where Be Use It Device?

Answer: A breaker is normally used to break a circuit. while breaking the circuit, the contact terminals will be separated. At the time of separation, an air gap is formed in between the terminals. Due to the existing current flow, the air in the gap is ionized and results in the arc. various mediums are used to quench this arc in respective CB’s. but in VCB the medium is vacuum gas. since the air in the CB is having vacuum pressure the arc formation is interrupted. VCB’s can be used up to kv.

Question 20. What Will Happen When Power Factor Is Leading In Distribution Of Power?

Answer: If there is a high power factor, i.e if the power factor is close to one:

losses in form of heat will be reduced,

cable becomes less bulky and easy to carry, and very cheap to afford, &

it also reduces overheating of transformers.

Question 21. What Is The One Main Difference Between Ups & Inverter? And Electrical Engineering & Electronics Engineering?

Answer: uninterrupted power supply is mainly used for short time .means according to ups VA it gives backup.

ups are also two types :

1. online.
2. offline.

online ups having a high volt and amp for long time backup with a high dc voltage. but ups start with 2v dc with 7 amp. but the inverter is started with 2v,24, dc to 36v dc and 20amp to the 80amp battery with longtime backup. 

Question 22. What Is 2 Phase Motor?

Answer: A two-phase motor is a motor with the starting winding and the running winding have a phase split.

e.g;ac servo motor.where the auxiliary winding and the control winding have a phase split of 90 degrees.

Question 23. What Is Power Factor? Whether It Should Be High Or Low? Why?

Answer: Power factor should be high in order to get smooth operation of the system. Low power factor means losses will be more.it is the ratio of true power to apparent power. it has to be ideally 1. if it is too low then cable overheating & equipment overloading will occur.

if it is greater than 1 then the load will act as a capacitor and starts feeding the source and will cause tripping. (if pf is poor ex: 0.17 to meet actual power load has to draw more current(V constant), result in more losses if pf is good.

ex: 0.95 to meet actual power load has to draw less current(V constant), result in less losses).

Question 24. There Are A Transformer And An Induction Machine. Those Two Have The Same Supply. For Which Device The Load Current Will Be Maximum? And Why?

Answer: The motor has max load current compare to that of transformer because the motor consumes real power.. and the transformer is only producing the working flux and it's not consuming.. hence the load current in the transformer is because of core loss so it is minimum.

Question 25. Explain The Working Principal Of The Circuit Breaker?

Answer: Circuit Breaker is one which makes or breaks the circuit. It has two contacts namely fixed contact & moving contact. under normal condition, the moving contact comes in contact with fixed contact thereby forming the closed contact for the flow of current. During abnormal & faulty conditions(when the current exceeds the rated value) an arc is produced between the fixed & moving contacts & thereby it forms the open circuit Arc is extinguished by the Arc Quenching media like air, oil, vacuum etc

Question 26. How Many Types Of Colling System It Transformers?

Answer :

1. ONAN (oil natural,air natural).
2. ONAF (oil natural, air forced).
3. OFAF (oil forced, air forced).
4. ODWF (oil direct, water forced).
5. OFAN (oil forced, air forced).

Question 27. What Is The Function Of Anti ­pumping In Circuit Breaker?

Answer: when the breaker is closed at one time by close push button, the anti-pumping contactor prevent reclose the breaker by close push button after if it already close.

Question 28. What Is Stepper Motor? what Are Its Uses?

Answer: Stepper motor is the electrical machine which acts upon input pulse applied to it. it is one type of synchronous motor which runs in steps in either direction instead of running in complete cycle.so, in automation parts it is used.

Question 29. Why The Capacitors Works On Ac Only?

Answer: Generally the capacitor gives infinite resistance to dc components(i.e., block the dc components). it allows the ac components to pass through.

Question 30. What Happens If I Connect A Capacitor To A Generator Load?

Answer: Connecting a capacitor across a generator always improves power factor, but it will help depends upon the engine capacity of the alternator, otherwise the alternator will be overloaded due to the extra watts consumed due to the improvement on pf. Secondly, don’t connect a capacitor across an alternator while it is picking up or without any other load.