25 Best Electrical Engineering interview questions and answers pdf

Electrical Engineering (EEE) Interview questions and answers pdf for freshers and experienced

1. What is your favourite subject in Electrical engineering?

Ans:
Normally they are looking for the subject in which their company is based on. Do not worry if you tell other than the subject of company. Be true to yourself. You will be trained once you will be recruited.

2. What was your project during Electrical engineering?

Ans:
They will looking for leadership. If you did project in group work, they will find out your leadership quality by related question.

3. What safety precautions should be observed while working in the workshop ?

Ans:

•       Keep shop floor clean, free from oil and other slippery materials.
•       Wear proper dress and avoid loose clothing and loose hair.
•       Wear shoes and avoid chapels.
•       Avoid playing, loose talk and funning inside the shop floor.
•       Keep good housekeeping and put all unnecessary items and rejected items in scrap box.
•       Learn everything about the machine before starting and clear all the doubts.
•       Keep a safe distance from rotating and sliding parts.
•       Never store inflammable materials inside or around the shop.
•       Never play with electricity, fire, parts with sharp edge etc.
•       Keep fire buckets and extinguishers ready for use.

4. What are the precautions to be taken to avoid fire ?

Ans:

•       The buckets along with sand should be placed inside the workshop.
•       Switches and other electrical parts must be made of fireproof material.
•       Carbon dioxide gas should be place at required points in special containers.
•       Fire extinguishers of suitable type should be placed at accessible places.

5. What do you mean by First Aid ?

Ans:

First Aid is immediate and temporary care given to a person who affected accidental injury or a sudden illness before the arrival of doctor.

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16. Operation carried out in Thermal power station?

Ans:

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

17. State the difference between generator and alternator

Ans:

Generator and alternator are two devices, which converts mechanical energy into electrical energy. Both have the same principle of electromagnetic induction, the only difference is that their construction. Generator persists stationary magnetic field and rotating conductor which rolls on the armature with slip rings and brushes riding against each other, hence it converts the induced emf into dc current for external load whereas an alternator has a stationary armature and rotating magnetic field for high voltages but for low voltage output rotating armature and stationary magnetic field is used.

18. What is difference between fuse and breaker?

Ans:

Fuses are burned at the time of over current flows in the circuit but breakers are just open(not burn) at the time of over current flow. Fuses are used in only one time but breakers are used by multiple number of times.

19. Brief description about Transformer?

Ans:

A transformer is a device that changes (transforms) and alternating potential difference (voltage) from one value to another value be it smaller or greater using the principle of electromagnetic induction.

20. Briefly explain different types of Transformers?

Ans:

Step-up Transformer

On a step-up transformer there are more turns on the secondary coil than the primary coil. The induced voltage across the secondary coil is greater than the applied voltage across the primary coil or in other words the voltage has been “stepped-up”.

Step-down Transformer

A step down transformer has less turns on the secondary coil that the primary coil. The induced voltage across the secondary coil is less the applied voltage across the primary coil or in other words the voltage is “stepped-down”.

21. Explain different losses in a transformer.

Ans:

There are two types of losses occurring in transformer:

• Constant losses or Iron losses: The losses that occur in the core are known as core losses or iron losses. Two types of iron losses are:

o eddy current loss

o Hysteresis loss.

These losses depend upon the supply voltage, frequency, core material and its construction. As long as supply voltage and frequency is constant, these losses remain the same whether the transformer is loaded or not. These are also known as constant losses.

• Variable losses or copper losses: when the transformer is loaded, current flows in primary and secondary windings, there is loss of electrical energy due to the resistance of the primary winding, and secondary winding and they are called variable losses. These losses depend upon the loading conditions of the transformers. Therefore, these losses are also called as variable losses.

22. Explain Power factor?

Ans:

The power factor of an AC electrical power system is defined as the ratio of the real power flowing to the load to the apparent power in the circuit.

23. State Ohm's Law?

Ans:

Ohm's law states that the electrical current (I) flowing in an circuit is proportional to the voltage (V) and inversely proportional to the resistance (R). Therefore, if the voltage is increased, the current will increase provided the resistance of the circuit does not change.

24. State Kirchhoff's Law?

Ans:

Kirchhoff's law 1  : states that the voltage changes around a closed path in a circuit add up to zero, where the voltage change DV = emf in going through a battery from - terminal to + terminal is considered to be positive, and the voltage change DV = I R in going through a resistor in the assumed direction of the current I is considered to be negative.

Kirchhoff's law 2 :   states that the sum of the currents entering any node (i.e., any junction of wires) equals the sum of the currents leaving that node.

25. State Maximum power transfer theorem?

Ans:

The Maximum power transfer theorem explains about the load that a resistance will extract from the network. This includes the maximum power from the network and in this case the load resistance is being is equal to the resistance of the network and it also allows the resistance to be equal to the resistance of the network. This resistance can be viewed by the output terminals and the energy sources can be removed by leaving the internal resistance behind.

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6. What is the principle of motor?

Ans:

Whenever a current carrying conductor is placed in an magnetic field it produce turning or twisting movement is called as torque.

7. Name different types of motors and its uses.

Ans:

Universal motor - Vacuum cleaners

Hysteresis motor - Phonographic appliances

Shaded pole motor - Vending machines

Capacitor split phase motors - Refrigerators

Cumulative motors - Rolling mills

DC shunt motors - Lathes

Synchronous motors - Power factor improvement

8. Which motor has high Starting Torque and Staring current ?

Ans:

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 load.

9. What is slip in an induction motor?

Ans:

Slip can be defined as the difference between the flux speed (Ns) and the rotor speed (N). Speed of the rotor of an induction motor is always less than its synchronous speed. It is usually expressed as a percentage of synchronous speed (Ns) and represented by the symbol ‘S’.

10. Why star delta starter is preferred with induction motor?

Ans:

Star delta starter is preferred with induction motor due to following reasons:

• Starting current is reduced 3-4 times of the direct current due to which voltage drops and hence it causes less losses.

• Star delta starter circuit comes in circuit first during starting of motor, which reduces voltage 3 times, that is why current also reduces up to 3 times and hence less motor burning is caused.

• In addition, starting torque is increased and it prevents the damage of motor winding.

11. Why series motor cannot be started on no-load?

Ans:

Series motor cannot be started without load because of high starting torque.

Series motor are used in Trains, Crane etc.

12. Why AC systems are preferred over DC systems?

Ans:

Due to following reasons, AC systems are preferred over DC systems:

a. It is easy to maintain and change the voltage of AC electricity for transmission and distribution.

b. Plant cost for AC transmission (circuit breakers, transformers etc) is much lower than the equivalent DC transmission. 

c. From power stations, AC is produced so it is better to use AC then DC instead of converting it.

d. When a large fault occurs in a network, it is easier to interrupt in an AC system, as the sine wave current will naturally tend to zero at some point making the current easier to interrupt.

13. What is the difference between delta-delta, delta-star transformer?

Ans:

Delta-delta transformer is used at generating station or a receiving station for Change of Voltage (i,e) generally it is used where the Voltage is high & Current is low.

Delta-star is a distribution kind of transformer where from secondary star neutral is taken as a return path and this configuration is used for Step down voltage phenomena.

14. What are the various kind of cables used for transmission?

Ans:

Cables, which are used for transmitting power, can be categorized in three forms:

• Low-tension cables, which can transmit voltage upto 1000 volts.

• High-tension cables can transmit voltage upto 23000 volts.

• Super tension cables can transmit voltage 66 kV to 132 kV.

15. What is vaccum circuit breaker?

Ans:

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 existing current flow the air in the gap is ionised and results in the arc. various mediums are used to quench this arc irrespective CB's. but in VCB the medium is vaccum gas. since the air in the CB is having vaccum pressure the arc formation is interrupted. VCB's can be used upto11kv.

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