Q. In a coil when current changes from 10A to 2A in time 0.1s, induced emf is 3.28 V. what is self –inductance of coil?
A) 4 H
B) 0.4 H
C) 0.04 H
D) 5 H
Explanation
(c) The induced emf is
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ e = - L\frac{di}{dt}$
Here, $di = (2 - 10)A = - 8\ A,\ dt = 0.1s,\ e = 3.28\ V.$
$\therefore\ \ \ \ \ \ \ \ \ 3.28 = \ - \frac{L( - 8)}{0.1}$
$\therefore\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ L = \frac{3.28 \times 0.1}{8} = 0.04H$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.