Question

A small bar magnet is moved through a coil at constant speed from one end to the other. Which of the following series of observations will be seen on the galvanometer $\text{G}$ attached across the coil?
Three positions shown describes:
$\left(1\right)$ The magnet's entry
$\left(2\right)$ Magnet is completely inside and
$\left(3\right)$ Magnet's exit.

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

Case (a) : When a bar magnet is entering with constant speed, flux $\left(\varphi \right)$ will change and an e.m.f. is induced, so the galvanometer will deflect in positive direction.

Case (b) : When magnet is completely inside, flux $\left(\varphi \right)$ will not change, so galvanometer will show null deflection.

Case (c) : When bar magnet is making on exit, again flux $\left(\varphi \right)$ will change and an e.m.f. is induced in opposite direction, so galvanometer will deflect in negative direction i.e., reverse direction.

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