In a moving iron instrument, if the operating current is increased from 1 A to 3 A, the torque will be _________.

Question

Question

This question was previously asked in

MPPGCL JE Electrical 28 April 2023 Shift 2 Official Paper

Answer 1

Concept

The torque in the MI instrument is given by:

\(T_d={1\over 2}I^2{dL\over dθ}\)

In a moving iron (MI) instrument, the torque is proportional to the square of the current.

T α I²

\({T_2\over T_1}=({I_2\over I_1})^2\)

Calculation

Given, I₂ = 3 A

I₁ = 1 A

\({T_2\over T_1}=({3\over 1})^2\)

\(T_2=9T_1\)

The torque increased to 9 times of initial value.