Question

A conducting wire frame is placed in a magnetic field, which is directed into the paper. The magnetic field is increasing at a constant rate. The directions of induced currents in wires $AB$ and $CD$ are

• A. $A$ to $B$ and $C$ to $D$
• B. $B$ to $A$ and $C$ to $D$
• C. $A$ to $B$ and $D$ to $C$
• D. $B$ to $A$ and $D$ to $C$

Answer 1

Answer: (D)

In the given question the magnetic field directed into the paper is increasing at a constant rate.
$\therefore $ Induced current should produce a magnetic field directed out of the paper. Thus current in both loops must be anticlockwise considering individually.

Induced emf on right side of loop will be more as area of its loop on right side is more.
$\left[\because e = - \frac{d \varphi}{d t} = - A \frac{d B}{d t}\right]$
$e \propto A$
Hence the net current induced in the complete loop will be along $DCBAD$ .