State Lenz’s law. A conducting rod of length $0.50\text{m}$ slides down smooth inclined rails that make an angle $30^{\circ }$ with the horizontal. The rails and the rod form a closed rectangular circuit in a uniform magnetic field $B=0.20\text{T}$ directed into the page. Indicate the direction of the induced current in the rod when it is moving downwards.

Step-by-step solution

1. Recall Lenz’s law: the induced emf generates a current whose magnetic field opposes the change in flux.
2. When the rod moves down, the area of the rectangular loop increases, so the magnetic flux into the page increases.
3. To oppose this increase, the induced magnetic field must be out of the page. By the right‑hand rule, a current producing an out‑of‑page field circulates clockwise when viewed from above.
4. In a clockwise circulation, the current in the moving rod goes from the upper rail toward the lower rail, i.e., downward.
5. State the direction as required.

Concept tested: Lenz’s law and direction of induced current

Published 7 September 2026 · How this solution was prepared and checked