A copper hoop is held in a vertical east-west plane in a uniform magnetic field whose field lines run along the north-south direction.The largest induced emf is produced when the hoop is:
A)rotated about a north-south axis
B)rotated about an east-west axis
C)moved rapidly, without rotation, toward the east
D)moved rapidly, without rotation, toward the south
E)moved rapidly, without rotation, toward the northwest

Question

Quizplus · Accepted Answer

When the hoop is rotated about an east-west axis, its area vector (perpendicular to the plane of the hoop) will continuously cut the magnetic field lines, resulting in maximum induced emf. If the hoop is rotated about a north-south axis, the area vector will always be parallel to the magnetic field lines and no emf will be induced. Rapid movement in any direction without rotation will not change the orientation of the area vector, so the induced emf will not be maximized.

A Copper Hoop Is Held in a Vertical East-West Plane