Free MCQs & Online Quiz Practice for Exams

Q: In Fleming's left-hand rule thumb always represents direction of:

A) Current flow

B) Induced e.m.f.

C) Magnetic field

D) Mechanical force

Q: The field at any point on the axis of a current-carrying coil will be:

A) Perpendicular to the axis

B) Parallel to the axis

C) At an angle of 45° with the axis

D) Zero

Q: When a coil rotates in a magnetic field the induced current in it:

A) Continuously changes

B) Remains same

C) Becomes zero

D) Becomes maximum

Q: In an A.C generator increasing the number of turns in the coil:

A) Decreases the electromotive force (e.m.f.)

B) Electromotive force (e.m.f.) remains same

C) Increases the electromotive force (e.m.f.)

D) Electromotive force (e.m.f.) becomes zero

Q: The device in which induced e.m.f. is statically induced e.m.f. is:

A) Transformer

B) AC generator

C) Alternator

D) Dynamo

Q: What is the coefficient of mutual inductance when the magnetic flux changes by 2×10⁻² Wb, and change in current is 0.01 A?

A) 2H

B) 3H

C) 1/2 H

D) Zero

Q: The induced e.m.f. in a coil is proportional to:

A) Magnetic flux through the coil

B) Rate of change of magnetic flux through the coil

C) Area of the coil

D) Product of magnetic flux and area of the coil

Q: In a coil current changes from 2A to 4A in 0.05s. If the average induced e.m.f. is 8 V then coefficient of self-inductance is:

A) 0.2 Henry

B) 0.1 Henry

C) 0.8 Henry

D) 0.04 Henry

Q: Which of the following quantities remain constant in a step-up transformer?

A) Current

B) Voltage

C) Power

D) Heat

Q: Step-up transformer has a transformation ratio of 3:2. What is the voltage in secondary if voltage in primary is 30 V?

A) 45V

B) 15V

C) 90V

D) 300V

Q: Eddy current is produced when:

A) A metal is kept in varying magnetic field

B) A metal is kept in steady magnetic field

C) Circular coil is placed in a steady magnetic field

D) Current is passed through a circular coil

Q: The r.m.s. value of a sine wave is 100 A. Its peak value is:

A) 70.7 A

B) 141.4 A

C) 150 A

D) 282.8 A

Q: A sine wave has a frequency of 50 Hz. Its angular frequency is (radian/second):

A) 100π

B) 50π

C) 25π

D) 5π

Q: The power factor of a purely resistive circuit is:

A) Zero

B) Unity

C) Lagging

D) Leading

Q: A capacitor is a perfect insulator for:

A) Direct current

B) Alternating current

C) Direct as well as alternating current

D) Induced e.m.f.

Q: The peak value of alternating current is 5 A. The mean square value of current will be:

A) 5 A

B) 2.5 A

C) 5√2 A

D) 5² A

Q: In a choke coil the reactance X_L and resistance R are related as:

A) X_L = R

B) X_L < R

C) X_L » R

D) X_L = ∞

Q: In AC system we generate sine wave form because:

A) It can be easily drawn

B) It produces least disturbance in electrical circuits

C) It is natural standard

D) Other waves cannot be produced easily

Q: An alternating voltage is given by 20 sin 157t. The frequency of alternating voltage is:

A) 50 Hz

B) 25 Hz

C) 100 Hz

D) 75 Hz

Q: In LR current, which one of the following statements is correct?:

A) L and R oppose each other

B) R value increases with frequency

C) The inductive reactance increases with frequency

D) The inductive reactance decreases with frequency