Question

An equilateral triangular loop $\text{ABC}$ having some resistance, is pulled with a constant velocity $v$ out of a uniform magnetic field $B$, directed into the paper. At time $t=0$, side $BC$ of the loop is at the edge of the magnetic field. The induced current $\left(i\right)$ versus time $\left(t\right)$ graph will be -

• A.
• B.
• C.
• D.

Answer 1

The correct option is B


After $t=0,$ as the triangular loop is pulled out, only the two sides remain in the magnetic field which will form an angle shaped open wire. Its effective length perpendicular to the magnetic field and velocity goes on decreasing with time at a constant rate.

Therefore, the induced emf $E=Blv$ versus times $t$, curve is a straight line with a constant, but negative slope as the effective length keep on decreasing at a constant rate.

After the whole loop is out of the magnetic field, no more emf will exist in the loop.

Also, induced current $i=\frac{E}{R}$ versus time $t$ curve will show similar behavior because resistance of loop $R$ is constant.


Hence, option $\left(\text{B}\right)$ is the correct answer.