Electrical Engineering Practice Impotent Questions Part 4

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45-If the speed of shunt motor to be controlled between zero and normal running speed N, the most practical way to achieve this would be to insert a resistance of suitable value in:

A. Parallel with the field

B. Series with the field

C. Parallel with the armature

D. Series with the armature

Ans: D. Series with the armature

46-A Charged body moving along a circle in magnetic field , a mass , velocity , and charge coulomb. What is the radius of its circular track?

A.

B.

C.

D.

Ans: D.

47-The current generated when a conductor moves across a magnetic field is called:

A. Active emf

B. Effective emf

C. Optimum emf

D. Induced emf

Ans: D. Induced emf

48-Two coils having equal resistances, but different inductances are connected in series. The time constant of the series combination is the:

A. Sum of the time constants of the individual

B. Average of the time constants of individual coils

C. Product of the time constants of individual coils

D. Geometric mean of the time constants of the individual coils

Ans: A. Sum of the time constants of the individual

49-Permeance is the reciprocal of

A. Flux density

B. Resistance

C. Ampere turns

D. Reluctance

Ans: D. Reluctance

50-A DC shunt motor is running at rated load and speed with rated supply voltage. If the supply voltage is halved, then the speed of the motor becomes:

A. Slightly more than the rated speed

B. Slightly less than the rated speed

C. Half of the rated speed

D. Double of the rated speed

Ans: B. Slightly less than the rated speed

51-Which of the following is not an integrating instrument?

A. Ampere hour meter

B. Watt hour meter

C. Volt meter

D. Both A & B

Ans: C. Volt meter

52-The main reason for connecting of a pulse transformer at the output stage of the Thyrister triggering circuit is to:

A. Amplify the power of the triggering pulse

B. Provide electrical isolation

C. Reduce the turn on time of the Thyrister

D. Avoid spurious triggering of the Thyrister due to noise

Ans: A. Amplify the power of the triggering pulse

53-One electron is moving in the electric and magnetic field. It will gain energy from:

A. Magnetic field

B. Electric field

C. Both A and B

D. Insufficient information

Ans: C. Both A and B

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