STATEMENT-1 A vertical iron rod has a coil of wire wound over it at the bottom end. An alternating current flows in the coil. The rod goes through a conducting ring as shown in the figure. The ring can float at a certain height above the coil. because STATEMENT-2 In the above situation, a current is induced in the ring which interacts with the horizontal component of the magnetic field to produce an average force in the upward direction.
(A)Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1✓ Correct
(B)Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1
(C)Statement-1 is True, Statement-2 is False
(D)Statement-1 is False, Statement-2 is True
Answer: (A)
Solution
Statement-1 is TRUE: This describes electromagnetic levitation. The alternating current in the coil creates a time-varying magnetic field, which induces eddy currents in the conducting ring (by Faraday's law). These induced currents interact with the magnetic field to produce a repulsive force that can levitate the ring.
Statement-2 is TRUE and is a correct explanation: The induced current in the ring interacts with the horizontal (radial) component of the magnetic field from the coil. By Lenz's law, the induced current opposes the change, creating a repulsive force. The horizontal component of the field, when interacting with the induced current, produces a net upward force that balances the weight of the ring.
Therefore, the answer is (A).
JEE Advanced · 2007 · 08 Apr 2007 · Paper 2 · Single correct option
