Q. If the coefficient of mutual induction of the primary and secondary coils of an induction coils is 5 H and current of 10 A is cut-off in $5 \times 10^{- 4}$s, the emf inducted (in volt) in the secondary coil is
A) $5 \times 10^{4}$
B) $1 \times 10^{5}$
C) $25 \times 10^{5}$
D) $5 \times 10^{6}$
Explanation
(b) The induced emf $e$ in the secondary is given by
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ e = - \frac{d\phi}{dt} = - M\frac{dl}{dt}$
or $\ \ \ \ \ \ \ \ \ \ \ \ \ \ |e| = M\frac{dI}{dt}$
$\therefore\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ |e| = 5 \times \frac{10}{5 \times 10^{- 4}} = 1 \times 10^{5}V$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.