A square conducting loop is situated such that it is vertical, in the xz-plane. The Earth's gravitational field points downward (in the $-\mathrm{z}$ 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 $\mathrm{z}: \mathrm{B}_{\mathrm{y}}(\mathrm{z})=\mathrm{B}_{0}(10 \mathrm{~m}-\mathrm{z})$. 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 counter-clockwise induced current.
C) There is a clockwise induced current.
D) There is no induced current.

Question

Quizplus · Accepted Answer

As the loop falls in the magnetic field, which varies with $\mathrm{z}$, there's a change in magnetic flux through the loop. According to Lenz's law, an induced current will oppose this change. Since the observer is looking from the $+y$ direction and the magnetic field decreases with $\mathrm{z}$, the induced current will be clockwise to oppose the reduction in magnetic flux.

A Square Conducting Loop Is Situated Such That It Is −z-\mathrm{z}−z

A Square Conducting Loop Is Situated Such That It Is $-\mathrm{z}$