A square conducting loop is situated such that it is vertical, in the xz-plane. The Earth's gravitational field points downward (in the -z direction). The loop is dropped and maintains its orientation in the xz-plane. A magnetic field pointing in the +y direction exists and is uniform with respect to time, but it varies as a function of z: B_y(z) = B₀(10 m − z). The loop is dropped and allowed to fall under the influence of gravitation. You observe the loop from the +y direction (i.e., looking toward the −y direction). Which of the following occurs? A) The situation is unclear because we do not know the initial conditions. B) There is a clockwise induced current. C) There is a counter-clockwise induced current. D) There is no induced current.

Question

Quizplus · Accepted Answer

The magnetic field decreases with increasing z (as the loop falls, z decreases, making the magnetic field stronger). According to Lenz's law, the induced current will oppose the change causing it, meaning it will try to decrease the magnetic field inside the loop. Viewed from the +y direction, a clockwise current would create a magnetic field opposing the increase, thus a clockwise induced current is correct.

A Square Conducting Loop Is Situated Such That It Is