The expected answers were:
(i) Deflecting device in a moving-coil works by the interaction of the field set up by the permanent magnet with the field set up by the current flowing through the coil.
(ii) Control device ensures that the deflecting device returns to its zero position after measurement with the aid of the restoring force in the hair spring.
- I(at f.s.d.) = 0.030A
V(at f.s.d.)= 0.090V
VT(voltage across terminals) = 100V
Rm =resistance of multiplier
Voltage across resistor = (100 – 0.090)V = 99.91V
Rm = 99.91 =3330.33
0.030A
The question was on Measuring Instruments. It was quite popular.
The performance was relatively satisfactory.
Many candidates did not do well in part(a) but most performed well in the calculation aspect of part(b).
