Question

Figure shows a square loop of side $5cm$ being moved towards right at a constant speed of $1cm/sec$. The front edge just enters the $20cm$ wide magnetic field at $t=0$. Find the induced emf in the loop at $t=2s$ and $t=10s$.

Answer 1

_{it is given that}

_{initial velocity $u=1cm/s$}

magnetic field $B=0.6T$

(a) At t = 2 s

Distance moved by the coil

$d=vt$

$=2cm=2\times {10}^{-2}m$

Area under magnetic field at t = 2 s

$A=2\times 5\times {10}^{-4}{m}^2$

$A={10}^{-3}{m}^2$

Initial flux = 0

Final flux $\varphi =BA=0.6\times {10}^{-3}$

Change in flux

$\Delta \varphi =0.6\times {10}^{-3}$

$emfe=\frac{\Delta \varphi }{\Delta t}$

$e=\frac{0.6\times {10}^{-3}}{2}$

$=3\times {10}^{-4}V$

(b) At t = 10 s

At this time coil is completely inside the coil so there is no change change in flux. So no emf will induce. Hence, induced emf at this time is zero.