Question

Assertion :Magnetic field $B$ (shown inwards) varies with time $t$ as shown. AT time $t_0$ induced current in the loop is clockwise. Reason: If rate of change of magnetic flux from a coil is constant, charge should flow in the coil at a constant rate.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Both assertion and reason are correct.

Induced emf=$-\frac{d\varphi }{dt}=-\frac{d\left(BA\right)}{dt}=-A\frac{dB}{dt}=constant$

Thus current in the loop is constant.

However the explanation for the assertion is Lenz Law. The current induced is such that the induced magnetic field avoids change of flux through the coil. The flux through the coil is into the plane and decreasing, thus the induced flux tends to maintain the flux into the plane, thus a clockwise current.