Question

Suppose the loop in Q.6.4 is stationary but the current feeding the electromagnet that produces the magnetic field is gradually reduced so that the field decreases from its initial value of 0.3 T at the rate of 0.02 TS^-1 . If the cut is joined and the loop has a resistance of 1.6Ω, how much power is dissipated by the loops as heat? What is the source of this power?

Answer 1

Induced e.m.f.

e = \(\frac{A(\phi_2-\phi_1)}{t}\)

= 8 × 2 × 10^-4 × 0.02 = 3.2 × 10^-5 V

Induced current

I = \(\frac{e}{R}=\frac{3.2\times10^{-5}}{1.6}\)

= 2 × 10^-5 A

Power Loss = I² r = (2 × 10^-5)² × 1.6 = 6.4 × 10^-10 W.

Source of this power is the external agent responsible for changing the magnetic field with time.