Electrical and Electronics Measurement Mcq

21. In a flux meter, the controlling torque is

(a) produced by weight attached to the moving coil.
(b) produced by spring.
(c) not provided at all.
(d) provided by crossed-coil mechanism.

22. What is connected across a flux meter for its effective functioning to measure magnetic flux density and also to compare the strengths of permanent magnets ?

(a) A resistor.
(b) A capacitor.
(c) A transformer.
(d) A search coil.

23. Analog panel meters basically measure.

(a) voltage.
(b) current.
(c) power.
(d) depends upon parameter.

24. Consider the following statements : In a measuring instrument,

1. linearity is more important than sensitivity.
2. high precision indicates high accuracy.
3. accuracy cannot be better than resolution.

Of these statements
(a) 1, 2 and 3 are correct.
(b) 1 and 2 are correct.
(c) 2 and 3 are correct.
(d) 1 and 3 are correct.

25. A moving coil galvanometer is made into a dc ammeter by connecting

(a) a low resistance across the meter.
(b) a high resistance in series with the meter.
(c) a pure inductance across the meter.
(d) a capacitor in series with the meter.

26. Consider the following statements about the D’Arsonval movement :

1. It is best suited for dc current measurement.
2. It responds to the average value of current.
3. It measures the rms value of ac currents.
4. It could be used for power measurements.

Which of these statements is/are correct ?
(a) Only 1.
(b) 1 and 2.
(c) 2 and 3.
(d) 1, 2, 3 and 4.

27. The internal resistance of the milli-ammeter must be very low for

(a) high sensitivity.
(b) high accuracy.
(c) maximum voltage drop across the meter.
(d) minimum effect on the current in the circuit.

28. A very accurate voltmeter gives inaccurate reading when used for measuring voltage across a low resistance because

(a) the meter sensitivity is too low.
(b) the meter sensitivity is too high.
(c) the voltmeter is taking too low current.
(d) the higher scale has been selected.

29. The effect of stray magnetic fields on the actuating torque of a portable instrument is maximum when the operating field of the instrument and the stray fields are

(a) perpendicular.
(b) parallel.
(c) inclined at 60°.
(d) inclined at 30°.

30. Which one of the following statements is correct ? Spiral springs are used in instruments to

(a) provide controlling torque.
(b) provide damping torque.
(c) lead the current to moving coil as well as to provide the controlling torque.
(d) provide linear deflection.

31. If the instrument has square law response, it can be used for the measurement of

(a) ac only.
(b) both ac and dc.
(c) dc only.
(d) none of the above.

32. A manganin swamp resistance is connected in series with a moving coil ammeter consisting of a milli-ammeter and a suitable shunt in order to

(a) minimize the effect of temperature variation.
(b) obtain large deflecting torque.
(c) reduce the size of the meter.
(d) minimize the effect of stray magnetic fields.

33. Consider the following statements associated with moving iron instruments:

1. These can be used in dc as well as ac circuits.
2. The scale is non-uniform.
3. The moving iron is placed in a field of permanent magnet.

Which of these statements are correct ?
(a) 1, 2 and 3.
(b) 1 and 2.
(c) 2 and 3.
(d) 1 and 3.

34. Eddy current damping cannot be used for moving iron instruments because

(a) weight of the instrument will increase.
(b) size of the instrument will increase.
(c) presence of permanent magnet will distort the magnetic field produced by the instrument and hence will affect its readings.
(d) eddy currents will pass through the iron thereby cause losses.

35. The moving iron instruments

(a) indicate the same values of measurand for both ascending and descending values.
(b) indicate higher value of measurand for descending values.
(c) indicate lower value of measurand for ascending values.
(d) may indicate any of the higher or lower value of measurand for ascending or descending values.

36. Hysteresis error, in moving iron instruments, may be reduced by using

(a) mumetal or permalloy.
(b) stainless steel.
(c) silver coating.
(d) high speed steel.

37. An unshielded moving iron voltmeter is used to measure the voltage in an ac circuit. If a stray dc magnetic field having a component along the axis of the meter coil appears, the meter reading would be

(a) unaffected.
(b) decreased.
(c) increased.
(d) either decreased or increased depending oil the direction of the dc field.

38. A spring-controlled moving iron voltmeter draws a current of 1 mA for full-scale value of 100 V. If it draws a current of 0.5 mA, the meter reading is

(a) 25 V
(b) 50 V
(c) 100 V
(d) 200 V

39. One of the control springs of a permanent magnet moving coil ammeter is broken. If connected in a circuit, the meter would read

(a) zero.
(b) half the correct value of the current.
(c) twice the correct value of the current.
(d) an indefinite figure.

40. A 0 – 10 A PMMC ammeter is not provided with any controlling mechanism and the moving parts are free to rotate. If a current of 1 A dc is passed through the moving coil the instrument

(a) will read 1 A.
(b) will read 10 A.
(c) pointer will continuously rotate.
(d) pointer will remain stationary.