Questions
21
Which of the following instruments indicate the instantaneous value of the electrical quantity being measured at the time at which it is being measured ?
Answer: Indicating instruments
22
A moving-coil permanent-magnet instrument can be used as flux-meter
Answer: by eliminating the control springs
24
Which of the following meters are not used on D.C. circuits
Answer: Induction meters
28
In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The
power factor of the load must be
Answer: 0.5
31
It is required to measure the true open circuit e.m.f. of a battery. The best device is
Answer: D.C. potentiometer
32
In an AC. co-ordinate potentiometer, the currents in the phase and quadrature potentiometer are adjusted to be
Answer: out of phase by 90°
33
In an Anderson bridge, the unknown inductance is measured in terms of
Answer: known capacitance and resistance
35
If the current in a capacitor leads the voltage by 80°, the loss angle of the capacitor is
Answer: 10°
36
In a Schering bridge the potential of the detector above earth potential is
Answer: a few volts only
37
A power factor meter has
Answer: one current circuit and two pressure circuits
38
In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at
Answer: 120°
39
In a Weston frequency meter, the magnetic axes of the two fixed coils are
Answer: perpendicular
40
The power factor of a single phase load can be calculated if the instruments available are
Answer: one voltmeter, one ammeter and one wattmeter
