Electromagnetism- Len'z Law

Three wire loops and an observer are positioned as shown in the figure. From the observer’s point of view, a current I flows counterclockwise in the middle loop, which is moving towards the observer with a velocity v. Loops A and B are stationary. This same observer would notice that

1. clockwise currents are induced in loop A and B
2. counterclockwise currents are induced in loop A and B
3. a clockwise current is induced in loop A, but a counterclockwise current is induced in loop B
4. a counterclockwise current is induced in loop A, but a clockwise current is induced in loop B
5. a counterclockwise current is induced in loop A, but no current is induced in loop B

(GR0177 #42)

Solution:

Lenz Law:  The tendency of nature to resist any change in magnetic flux passing through a loop of wire.

When the middle loop moving toward the observer A:

• Loop A feels an increasing current and resists the change of magnetic flux by inducing a decreasing current in the opposite direction (clockwise).
• Loop B feels a decreasing current and resists the change of magnetic flux by inducing an increasing current in the same direction (counter-clockwise).

Answer: C