Basic Electrical Engineering MCQ And Answers For SPPU Exam 2020 Part-6

1. A conductor carries 125 amperes of current under 60° to a magnetic field of 1.1 tesla.

The force on the conductor will be nearly

1. 50 N
2. 120 N
3. 240 N
4. 480 N

Ans: b

2. Find the force acting on a conductor 3m long carrying a current of 50 amperes at right

angles to a magnetic field having a flux density of 0.67 tesla.

1. 100 N
2. 400 N
3. 600 N
4. 1000 N

Ans: a

3. The co-efficient of coupling between two air core coils depends on

1. self-inductance of two coils only
2. mutual inductance between two coils only
3. mutual inductance and self inductance of two coils
4. none of the above

Ans: c

4. An average voltage of 10 V is induced in a 250 turns solenoid as a result of a change in flux which occurs in 0.5 second. The total flux change is

1. 20 Wb
2. 2 Wb
3. 0.2 Wb
4. 0.02 Wb

Ans: d

5. A 500 turns solenoid develops an average induced voltage of 60 V. Over what time interval must a flux change of 0.06 Wb occur to produce such a voltage ?

a.0.01 s

2. 0.1 s
3. 0.5 s
4. 5 s

Ans: c

6. Which of the fpllowing inductor will have the least eddy current losses ?

1. Air core
2. Laminated iron core
3. Iron core
4. Powdered iron core

Ans: a

7. A coil induces 350 mV when the current changes at the rate of 1 A/s. The value of inductance is

1. 3500 mH
2. 350 mH
3. 250 mH
4. 150 mH

Ans: b

8. Two 300 uH coils in series without mutual coupling have a total inductance of

1. 300 uH
2. 600 uH
3. 150 uH
4. 75 uH

Ans: b

9. Current changing from 8 A to 12 A in one second induced 20 volts in a coil.

The value of inductance is

1. 5 mH
2. 10 mH
3. 5 H
4. 10 H

Ans: c

10. Which circuit element(s) will oppose the change in circuit current ?

1. Resistance only
2. Inductance only
3. Capacitance only
4. Inductance and capacitance

Ans: b

11. A crack in the magnetic path of an inductor will result in

1. unchanged inductance
2. increased inductance
3. zero inductance
4. reduced inductance

Ans: d

12. A coil is wound on iron core which carries current I. The self-induced voltage in the coil is not affected by

1. variation in coil current
2. variation in voltage to the coil
3. change of number of turns of coil
4. the resistance of magnetic path

Ans: b

13. A moving magnetic field will produce the same effect as a conductor that is moving.

1. Yes
2. No

Ans:a

14. The polarity of the induced voltage can be determined by using the left-hand generator rule.

1. Yes
2. No

Ans: a

1. Diamagnetic materials
2. Ferrimagnetic materials
3. Antiferromagnetic materials
4. Antiferrimagnetic materials

Ans: c

21.The attraction capacity of electromagnet will increase if the

1. core length increases i
2. core area increases
3. flux density decreases
4. flux density increases

Ans: d

22.Which of the following statements is correct ?

1. The conductivity of ferrites is better than ferromagnetic materials
2. The conductivity of ferromagnetic materials is better than ferrites
3. The conductivity of ferrites is very high
4. The conductivity of ferrites is same as that of ferromagnetic materials

Ans: a

23.Temporary magnets are used in

1. loud-speakers
2. generators
3. motors
4. all of the above

Ans: d

24.Main causes of noisy solenoid are

1. strong tendency of fan out of lami-nations at the end caused by repul¬sion among magnetic lines of force
2. uneven bearing surface, caused by dirt or uneven wear between moving and stationary parts
3. both of above
4. none of the above

Ans: c

25.Strength of an electromagnet can be increased by

1. increasing the cross-sectional area
2. increasing the number of turns
3. increasing current supply
4. all above methods

Ans:

26.Core of an electromagnet should have

a. low coercivity

6.high susceptibility

3. both of the above
4. none of the above

Ans: c

27.Magnetism of a magnet can be destroyed by

1. heating
2. hammering
3. by inductive action of another magnet