Question

The diagram above shows a rectangular wire loop moving at a constant velocity in the direction of the red arrow. The loop is entirely in the uniform magnetic field pictured, and it stays entirely i the filed. The magnetic field is represented by the blue dots which shows that the magnetic field points of the page.
As the loop continues to move in the magnetic field what happens in the wire loop?

• A. Conventional current flows around the wire loop in a clockwise direction and has a constant value.
• B. Conventional current flows around the wire loop in a clockwise direction and increases in value as the loop moves further into the magnetic field.
• C. Conventional current flows around the wire loop in a counter clockwise direction and has a constant value.
• D. Conventional current flows around the wire loop in a counter clockwise direction and increases in value as the loop moves further into the magnetic field.
• E. No current flows in the wire loop.

Answer 1

The correct option is E No current flows in the wire loop.

We must understand Lenz's law and magnetic fields around current-carrying loops or coils to answer this question.

Lenz's law says that the current induced in a coil or loop of wire by a changing magnetic field or flux will always be in such a direction as to produce a magnetic field whose field or flux will oppose the change in magnetic field or flux that produced the current.

In this case, we must notice that as the loop moves, the flux through the loop does not change. The number of field lines would remain the same–if we represented them as very tightly packed. The flux would only change while the loop enters or leaves the magnetic field.

Since in this case there is no changing flux, there is no current in the loop, hence option "E" is right.