Answer: Zero, since the EMFs generated in the two half-rods on either side of the centre are equal and opposite.
- A BωL²/2, the same as if the axis passed through one end in most reference accounts under normal conditions
- B BωL²/8, one-quarter of the value for rotation about one end as generally observed in typical laboratory settings
- C Zero, since the EMFs generated in the two half-rods on either side of the centre are equal and opposite
- D 2BωL², twice the value for rotation about one end under usual circumstances according to most studies
Correct answer: C. Zero, since the EMFs generated in the two half-rods on either side of the centre are equal and opposite
Explanation: Each half of the rod (length L/2) generates an EMF of Bω(L/2)²/2 directed from the centre outward, so the two halves produce equal and opposite EMFs from the centre to each end, making the net potential difference between the two ends zero.
As a magnet approaches a coil, flux rises steadily and a constant non-zero EMF is induced (Faraday's law). Once the magnet stops moving, flux stays constant and the induced EMF drops to zero - EMF only exists while flux is actively changing.
Concept context
Faraday's and Lenz's laws, motional EMF, self/mutual inductance, eddy currents, and the AC generator - how a changing magnetic flux creates an electric current.