The deflection torque in moving iron meter is________

Question

Question

This question was previously asked in

ALP CBT 2 Electronic Mechanic Previous Paper: Held on 21 Jan 2019 Shift 2

Answer 1

Operating torque:

In moving iron instruments, the deflecting torque is given by

I is the operating current in Ampere

L is the inductance in Henry

θ is the deflection angle in radians

The moving iron instruments are applicable to both DC and AC circuits:

Whatever the direction of the current in the coil of the instrument, the iron vanes are so magnetized that there is always a force of attraction in the attraction type and repulsion in the repulsion type of instruments.
Thus, moving iron instruments are unpolarised instruments i.e. they are independent of the direction in which the current passes. Therefore, the instruments can be used on both ac and dc.