Question

The square coil shown in the figure has a side of $30\text{cm}$ and $20$ turns of wire on it. It is moving to the right at a speed of $3{\text{ms}}^{-1}$ as shown, inside there exists a magnetic field whose left boundary is $\text{KL}.$ The induced e.m.f. and the direction of induced current in the coil :
(i) At the instant shown and
(ii) When the coil is completely inside the field region

• A. $\left(i\right)7.2\text{V}\text{anticlockwise}\left(ii\right)7.2\text{V}\text{clockwise}$
• B. $\left(i\right)7.2\text{V}\text{clockwise}\left(ii\right)7.2\text{V}\text{anticlockwise}$
• C. $\left(i\right)7.2\text{V}\text{anticlockwise}\left(ii\right)\text{Zero}$
• D. $\left(i\right)7.2\text{V}\text{clockwise}\left(ii\right)\text{Zero}$

Answer 1

The correct option is C $\left(i\right)7.2\text{V}\text{anticlockwise}\left(ii\right)\text{Zero}$

(i) The induced emf $E=nBlv$

$=20\times 0.4\times 0.3\times 3=7.2\text{V}$

By Flemings right-hand rule, the direction of current is from $\text{c to b (anticlockwise).}$

(ii) When the coil is fully inside the field, net change in flux linked with the loop is zero. Hence, no emf is induced.

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(C\right)$ is the correct answer.