Measurements

Explanation of question 2

The deflecting torque on the coil of a moving coil instrument is dependent upon the

1. current in the coil
2. strength of the magnetic field from the permanent magnet
3. scale calibration
4. 1, 2 and 3

The answer is :- 4 The deflecting torque is produced by the interaction of the magnetic fields produced by the current in the coil and that due to the permanent magnet, i.e. a and b. For a particular instrument, b will be fixed.