Question

A square wire loop of $10.0cm$ side lies at right angles to a uniform magnetic field of $7T$. A $10V$ light bulb is in series with the loop as shown in figure. The magnetic field is decreasing steadily to zero over a time interval $\Delta t$. For what value if $\Delta t$ (in $ms$), the bulb will shine with full brightness?

Answer 1

$\varphi =BA$

$E=\frac{d\varphi }{dt}=A\frac{dB}{dt}$

given
$E=10V$

$A\frac{B}{t}=10$

$t=\frac{AB}{10}$

$t=\frac{{0.1}^2\times 7}{10}=7ms$