A light disc made of aluminium (a nonmagnetic material) is kept horizontally and is free to rotate
about its axis as shown in the figure. A strong magnet is held vertically at a point above the disc
away from its axis. On revolving the magnet about the axis of the disc, the disc will (figure is
schematic and not drawn to scale)-
Select the correct option:
A
rotate in the direction opposite to the direction of magnet’s motion
B
rotate in the same direction as the direction of magnet’s motion
C
not rotate and its temperature will remain unchanged
D
not rotate but its temperature will slowly rise
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
When the magnet is moved, it creates a state where the plate moves through the magnetic flux, due
to which an electromotive force is generated in the plate and eddy currents are induced. These
currents are such that it opposes the relative motion disc will rotate in the direction of rotation of
magnet.
Note : This apparatus is called Arago's disk.
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