Question

Figure shows a suare loop of side 5 cm being moved towards right at a constant speed of 1 cm.s. The front edge enters the 20 cm wide magnetic field at t= 0. Find the emf induced in the top at

(a) t = 2 s,

(b) t = 10 s,

(c) t = 22 s. and

(d) t = 30 s.

Answer 1

Here u = 1 cm/s, b = 0.6 t

(a) At t = 2 sec.,

Distance moved = $2\times 1cm/s=2cm$

e = $\frac{d\Phi }{dt}$

= $\frac{0.6\times (2\times 5-0)\times {10}^{-4}}{2}$

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

(B) At t = 10 sec,

Distance moved = $10\times 1=10cm$

The flux linked does not change with time

$\therefore$ e = 0

(c) At t = 22 sec.

Distance moved = $22\times 1=22cm.$

The loop is moving out of the field ad 2 cm outside;

e = $\frac{d\Phi }{dt}=B\times \frac{dA}{dt}$

= $\frac{0.6\times (2\times 5\times {10}^{-4})}{2}$

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

(d) At t = 30~sec

The loop is totally outside and flux linked

= 0

$\therefore$ e = 0