Mock test-6

Electrical Engineering (Code: 23/10/17)

(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 energy stored in the electric field of a capacitor C with a voltage V across it, is

(a) 𝑉2

𝐶

(b) CV

(c) 1

2

𝑉2

𝐶

(d) 1

2𝐶𝑉2

2. The circuit component that opposes an instantaneous change in the circuit current is

(a) Resistance

(b) Capacitance

(c) Inductance

(d) None

3. The reciprocal of j is

(a) J

(b) 0

(c) –j

(d) 1

4. The inductor is

(a) Active element

(b) A linear element

(c) Unilateral element

(d) None

5. The frequency of a.c. is doubled .what happens is to the capacitance reactance?

(a) Become half

(b) Become double

(c) No change

(d) None

6. Which of the following elements is bilateral?

(a) Constant current source

(b) Constant voltage source

(c) Non-electrolytic capacitor

(d) None

7. The electrical mains is 240v 50Hz .the equation for the instantaneous voltage is

(a) 240

√2sin100𝞹t

(b) 240√2𝑠𝑖𝑛100𝞹t

(c) 240

√2sin50𝞹t

(d) 240√2𝑠𝑖𝑛50𝞹t

8. The frequency of ac is double, what happens to the inductive?

(a) Become half

(b) No change

(c) become double

(d) None

9. The average power absorbs by passive element is

(a) Always zero

(b) Always positive

(c) Always negative

(d) Zero or positive but never negative

10. Which of the following is a linear and bilateral element?

(a) Resistor

(b) Electron tube

(c) Transistor

(d) None

11. Which bulb has the minimum resistance?

(a) 110v ,60w

(b) 110v ,100w

(c) 220v ,60w

(d) 220v ,100w

12. What type of core is used in a high frequency transformer?

a. Open iron core

b. Air core

c. Closed iron core

d. None of these

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. In transformer, Z1 and Z2 are related as

(a) Z1> Z2

(b) Z1< Z2

(c) Z1= Z2

(d) None

21. 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

22. 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

23. An ammeter can be used as voltmeter by using with it

(a) Shunt of high resistance

(b) Series of high resistance

(c) Shunt of low resistance

(d) Series of low resistance

24. In a circuit containing R,L and C, power loss takes place in

(a) L only

(b) C only

(c) R only

(d) All of above

25. Power factor of electric incandescent lamp is

(a) Lagging

(b) Unity

(c) Leading

(d) Zero

26. Full safety of an electrical installation is ensured when it is provided with

(a) Proper insulation

(b) Good earthing

(c) Proper fuse in circuit

(d) All of above

27. To start a dc shunt motor below the rated speed, a resistance is inserted in series with

(a) Motor

(b) Armature

(c) Field winding

(d) Any of the above

28. For transmission over a long distance, high voltage is preferred because

(a) It requires conductor of less cross section area

(b) Copper loss is less

(c) Voltage regulation is better

(d) All of the above

29. The meter constant of energy meter is given by

a. Rev./kW

b. Rev./kWh

c. Rev./watt

d. None of these

30. 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

31. 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

32. The speed of energy meter can be controlled by

a. Series magnet

b. Braking magnet

c. Shunt magnet

d. Shading magnet

33. 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

34. 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

35. Which of the following theorem use as equivalent voltage generator in circuit analysis

a. Norton’s theorem

b. Maximum power transfer theorem

c. Thevenin’s theorem

d. Superposition theorem

36. Condition of maximum power transfer apply to

a. Current source alone

b. Voltage source alone

c. Both current and voltage source

d. None of these

37. A voltage source having a high input impedance and a very low output impedance is

known as

a. Constant current source

b. Constant power source

c. Constant voltage source

d. None of these

38. Maximum power is transferred from source when load impedance is

a. Equal to source impedance

b. Equal to zero

c. Equal to half of source impedance

d. None of these

39. Norton’s equivalent circuit consists of

a. Voltage source in parallel with impedance

b. Current source in series with impedance

c. Voltage source in series with impedance

d. Current source in parallel with impedance

40. The armature resistance of a 200V shunt motor is 0.4Ω and no-load armature is 2A. with

load , its armature current is 50A and speed is 1200rpm. The load speed would be.

a. 1500rpm

b. 1460rom

c. 1330rpm

d. 1200rpm

41. The highest speed attained by a dc shunt motor is

a. Higher than the rated speed at rated flux

b. Equal to no-load speed at rated flux

c. Lower than no-load speed at rated flux

d. None of these

42. The dummy coil in dc machine is used to

a. Eliminate reactance voltage

b. Eliminate armature reaction

c. Bring about mechanical balance of armature

d. Eliminate harmonics developed in the machine

43. The function of starter in a dc machine is to

a. Avoid the excessive current at starting

b. Increase the speed of rotation

c. Decrease the speed of rotation

d. None of these

44. An external resistance is added in the series with the field of a dc shunt motor

a. To reduce the speed of the motor

b. To increase the speed of the motor

c. To reduce the armature current drawn by the motor

d. To reduce the losses

45. As the load is increased the speed of a dc shunt motor will

a. Remain constant

b. Increase proportionally

c. Increase slightly

d. Reduce slightly

46. If the current in the armature of a dc shunt motor is reduced to 5%, the torque of the

motor will be

a. 50% of the previous value

b. 25% of the previous value

c. 150% of the previous value

d. 125% of the previous value

47. When a pentavalent impurity is added to a pure semiconductor, it becomes

a. P-type semiconductor

b. N-type semiconductor

c. PN junction

d. Intrinsic

48. Addition of trivalent impurity to a pure semiconductor creates many

a. Free electrons

b. Valence electrons

c. Holes

d. All 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

Mock test will be available every week on www.electricaledu.com

http://www.electricaledu.com/