Question

In a moving iron meter, the deflection torque is proportional to?

(a) Square of the current through the coil

(b) Current through the coil

(c) Sine of measurand

(d) The Square root of the measurand

This question was posed to me in class test.

My question is from Advanced Problems on Filters in portion Filters and Attenuators of Network Theory

Answer 1

The correct choice is (a) Square of the current through the coil

The explanation: We know that Td = \(\frac{1}{2} I^2  \frac{dl}{dθ}\)

Hence, the deflection torque is proportional to the square of the current through the coil.