Mock test-7

Electrical Engineering (Code: EE/5/11)

(Questions are based on SSC(JE), PSC(JE), BSNL(TTA), WBSEDCL, WBSETCL, WBPDCL, CIL State

and Central Service Examinations)

Note: Answer will be available after one week

Time Allowed: 1hours Maximum Marks: 50

1. The use of higher flux density in transformer design

a. Increase the weight per kVA

b. Decreases the weight per kVA

c. Increase the weight per kW

d. Decreases the weight per kW

2. The induced emf in the secondary of a transformer will depend on

a. Frequency of the supply only

b. Number turns in secondary only

c. Maximum flux in the core only

d. Frequency, flux and number of turns in the secondary

3. Two transformers are operating in parallel, they will share the load depending upon

their

a. Efficiency

b. Rating

c. Leakage reactance

d. Per-unit impedance

4. Why there is an enamel layer coated over the laminations of the transformer core

a. To decrease the hum

b. To attain adhesion between the laminations

c. To insulate the lamination against each other

d. To prevent the corrosion of the laminations

5. The full load copper loss and iron loss of a transformer are 6400watts and 5000watts

respectively. The copper loss and iron loss at half load will be

a. 3200watts and 2500watts

b. 3200watts and 5000watts

c. 1600watts and 1250watts

d. 1600watts and 5000watts

6. In a 3-phase, 4-wire unbalanced system, the current in the neutral wire is 12A. the zero

sequence current in each phase is

(a) 12A

(b) 6A

(c) 24A

(d) 4A

7. In a synchronous generator the positive sequence impedance(Z1) and negative sequence

impedance (Z2) are related as

(a) Z1= Z2

(b) Z1> Z2

(c) Z1< Z2

(d) None

8. In transformer, Z1 and Z2 are related as

(a) Z1> Z2

(b) Z1< Z2

(c) Z1= Z2

(d) None

9. The short circuit kVA is maximum when fault occurs

(a) Near the generator

(b) At the end of transmission line

(c) In the middle of transmission line

(d) None

10. Current limiting reactor in power system have

(a) Large resistance and low reactance

(b) Large reactance and low resistance

(c) Large reactance and resistance

(d) None

11. In a 3-phase, 4-wire unbalanced system, the current in the neutral wire is 18A. the

magnitude of zero sequence current is

(a) 18A

(b) 9A

(c) 6A

(d) 3A

12. The most severe unsymmetrical is

(a) Single line to ground fault

(b) Line to line fault

(c) Double line to ground fault

(d) None

13. Three resistances each of RΩ are connected to form a triangle. The resistance between

any two terminal will be

(a) RΩ

(b) 3

2𝑅Ω

(c) 3𝑅Ω

(d) 2

3𝑅Ω

14. When sinusoidal voltage is applied across a pure capacitor, the current in the capacitor

(a) Lags the voltage by 900

(b) Leads the voltage by 900

(c) Is in phase with applied voltage

(d) None

15. The peak factor of a sine wave is

(a) 1.11

(b) 1.414

(c) 2

(d) 1.5

16. The property of material which opposes the creation of magnetic flux in it ,is called

(a) Permeability

(b) Intensity

(c) Magnetizing force

(d) Reluctance

17. The unit of flux density is

(a) Tesla

(b) 𝐴𝑇

𝑚2

(c) 𝑊𝐵

𝑚2

(d) 𝑛𝑜𝑛𝑒

18. The energy stored in a magnetic field is given by (L=self inductance, I=current)

(a) L2I

(b) 1

2𝐿𝐼2

(c) 1

2𝐿𝐼

(d) 1

2𝐿2𝐼

19. The Megger is used to measure

(a) Current

(b) Electric energy

(c) Insulation resistance

(d) Low resistance

20. Wattmeter is used to measure

(a) Current

(b) Resistance

(c) Power

(d) Voltage

21. An alternating current is given by i=10sin314t. the time taken by the current to reach a

value of 10A is

(a) 0.025sec

(b) 0.05sec

(c) 0.01sec

(d) 0.02sec

22. A wire is stretched to its double the length ,the new resistance will be

(a) 4 time the original resistance

(b) Double the original resistance

(c) Half the original resistance

(d) One-fourth the original resistance

23. When the frequency of supply voltage is increased the resistance of an inductor will

(a) Increase

(b) Decrease

(c) Remain same

(d) None

24. A galvanometer can be used for measuring current and voltage of a circuit by

a. Shunt only

b. Connecting high value of resistance in series only

c. Shunt for measuring current and high resistance in series for measuring voltage

d. None of these

25. The most commonly used single phase energy meter

a. Dynamometer type

b. Electrostatic type

c. Induction type

d. Moving coil type

26. The meter constant of energy meter is given by

a. Rev./kW

b. Rev./kWh

c. Rev./watt

d. None of these

27. The series magnet of a single phase energy meter consists of a coil of

a. Thin wire of few turns

b. Thick wire of few turns

c. Thick wire of more turns

d. Thin wire of more turns

28. The pressure coil consists of

a. More number of turns of fine wire

b. Less number of turns of fine wire

c. Less number of turns of thick wire

d. More number of turns of thick wire

29. The speed of energy meter can be controlled by

a. Series magnet

b. Braking magnet

c. Shunt magnet

d. Shading magnet

30. The creeping error in single phase energy meter can be minimized by

a. Adjusting barking magnet

b. Use of short circuited loops on the outer limbs of the shunt magnet

c. Drilling two holes in the disc on the opposite side of the spindle

d. Adjusting the shaded band

31. Electrostatic instruments are suitable for the measurement of

a. AC and DC voltage

b. AC voltage and current

c. DC voltage and current

d. AC voltage only

32. Electrostatic instrument work on the principle of

a. Repulsion of unlike poles

b. Attraction of like poles

c. Attraction between positive and negative

d. Repulsion between negative chares

33. High ac voltage are usually measured with a

a. Voltmeter and current transformer

b. Millivoltmeter and shunt

c. Voltmeter and multiplier

d. Voltmeter and potentiometer

34. In the ac circuit the watt less lagging component of the is responsible for the production

of

(a) Power

(b) Electrical field

(c) Magnetic

(d) None

35. In a pure inductive circuit

(a) The reactive power is zero

(b) The apparent power is zero

(c) Actual power is zero

(d) None

36. A series RL circuit draws 1A current from a 100V 60Hz supply .if the value of R is 100Ω ,

the value of L must be

(a) Zero

(b) 100mH

(c) 1H

(d) None

37. A load of( 25+j25)Ω is connected across a (75-j50)v ac supply .the current is

(a) (0.5+j2.5)A

(b) (0.5-j2.5)A

(c) (-0.5+2.5)A

(d) None

38. A circuit of zero lagging power factor behaves as

(a) Inductive ckt

(b) Capacitive ckt

(c) R-L circuit

(d) R-L-C circuit

39. In an ac circuit, if the voltage is V=(a-jb) and the current is I=(c+jb). The power is

(a) Ac+ad

(b) Ac+bd

(c) Bc-ad

(d) Bc+ad

40. Superposition theorem applies to

a. DC circuit only

b. AC circuit only

c. AC and DC with voltage source

d. AC and DC with voltage and current sources or mixed type sources

41. Thevenin’s theorem is valid for a network containing only

a. Linear circuit

b. Non-linear circuit

c. Reactive circuit

d. Resistance

42. Applying maximum power transfer theorem, if the source impedance is equivalent to

R+jX, the load impedance will be

a. R only

b. R+jX only

c. R – jX only

d. 0-jX only

43. What happens if the field winding of a running shunt motor suddenly breaks open?

a. Its speed slow down

b. Its speed becomes dangerously high

c. It gives out sparks

d. It stops at once

44. If the back emf in a dc motor is absent, then

a. Motor will run at very high speed

b. Motor will run at very slow speed

c. Motor will not run at all

d. Motor will burn

45. The field flux of a dc motor can be controlled to achieve

a. The speed lower than the rated speed

b. The speed higher than the rated speed

c. The speed at rated speed

d. None of these

46. If the field of the dc shunt motor is opened

a. It will continue to run at rated speed

b. The of the motor will become very high

c. The motor will stop

d. None of these

47. Which of the following motors is used for rolling mills?

a. DC shunt motor

b. DC cummulative compound motor

c. DC series motor

d. DC differential compound motor

48. What will happen if the supply terminals of a dc shunt motor are interchanged?

a. Motor will stop

b. Motor will run at its normal speed in the same direction as it was running

c. The direction of rotation will reverse

d. None of these

49. A pentavalent impurity is called

a. Donor impurity

b. Acceptor impurity

c. Ionic impurity

d. None of these

50. PN junction acts as a

a. Unidirectional switch

b. Bi-directional switch

c. Controlled switch

d. None of these

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