Question

Magnetic field through a coil having $200$ turns and cross - sectional area $0.04m^2$ changes from $0.1Wb{m}^{-2}$ to $0.04Wb{m}^{-2}$ in $0.02sec$. Find the induced emf

Answer 1

$N=200;A=0.04m^2;B_1=0.1Wb{m}^{-2}$
$B_2=0.04Wb{m}^{-2};t=0.02;e=?$
$e=\frac{d\varphi }{dt}=\frac{-d\left(\varphi \right)}{dt}$
$e=-\frac{d}{dt}\left(NBA\right)=-NA\frac{dB}{dt}=-NA\frac{B_2-B_1}{dt}$
$=-200\times 4\times {10}^{-2}\times \frac{(0.04-0.1)}{0.02}$
$e=24V$