Question

The magnetic field in a region between the poles of an electromagnet is uniform at any time, but its magnitude is increasing at the rate of $ 0.02\,T/s $ . A conducting loop is placed in this region, whose plane is perpendicular to the direction of magnetic field. Calculate the emf induced and induced current in the loop. Take cross-section area of loop as $ 120\,cm^{2} $ and resistance of loop as $ 5\Omega $ .

• A. 0.48 V, 0.0096 mA
• B. 0.48 mV, 0.0096 mA
• C. 0.24 mV, 0.048 mA
• D. 0.24 mV, Zero

Answer 1

Answer: (C)

Induced emf
$e=-\frac{d \phi}{d t}=-A \times \frac{d B}{d t} $
$=-120 \times 10^{-4} \times 0.02$
Negative sign tells about the direction (polarity).
Also, $i=\frac{e}{R}=\frac{0.24}{5} $
$=0.048\, m A$