During a 72-ms interval, a change in the current in a primary coil occurs. This change leads to the appearance of a 6.0-mA current in a nearby secondary coil. The secondary coil is part of a circuit in which the resistance is 12 Ω. The mutual inductance between the two coils is 3.2 mH. What is the change in the primary current?

so change in primary current is 1.620 A

Explanation:

Given data

current I = 6.0-mA = 6 * 10^ (-3) A

resistance R = 12 Ω

mutual inductance M = 3.2 mH = 3.2 * 10^ (-3) H

dt = 72-ms = 72 * 10^ - (3) s

to find out

change in the primary current

solution

we know that

Electric and magnetic fields in secondary coil = mutual inductance * change in primary current / dt ... 1

and we know also that Electric and magnetic fields in secondary coil = resistance * current

so = 6 * 10^ (-3) * 12 = 72 * 10^ (-3) volts

so that we say

change in primary current from equation 1

change in primary current = Electric and magnetic fields in secondary coil * dt / mutual inductance

change in primary current = 72 * 10^ (-3) * 72 * 10^ (-3) / 3.2 * 10^ (-3)

change in primary current = 1.620

so change in primary current is 1.620 A