Measurements and Instrumentation

51

Assertion (A): Hall effect is observed in all metals but is very appreciable in semiconductors.

Reason (R): Hall effect transducer is very suitable for measurement of magnetic flux density.

A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true R is false
D. A is false R is true

52

Consider the following galvanometers

  1. D'Arsonval
  2. Ballistic
  3. Vibration
Which of these are permanent magnet moving coil instruments?

A. 1 and 2 only
B. 1, 2 and 3
C. 2 and 3 only
D. 1 and 3 only

53

A direct current can be measured

A. directly by dc potentiometer
B. by dc potentiometer in conjunction with a standard resistance
C. by dc potentiometer in conjunction with volt ratio box
D. none of the above

54

Assertion (A): In two wattmeter method of 3 phase power measurement, one of the wattmeters would read negative if power factor of load is less than 0.5.

Reason (R): In two wattmeter method of 3 phase power measurement, both the wattmeters would show equal readings if power factor of load is unity.

A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true R is false
D. A is false R is true

55

In a megger the moving coil meter has a permanent magnet.

A. True
B. False