1. When a magnet is dropped into a cylindrical conducting tube, it does not fall

Question

1.              When a magnet is dropped into a cylindrical conducting tube, it does not fall with usual acceleration of graity. How can this be explained?

A.     Air friction in the narrow tube slows it down.

B.     The powerful magnetic field induces a magnetic field in the tube, and this creates a force repelling the magnet.

C.     An electromagnetic wave in generated that propagates in the direction opposite to the direction of motion of the falling magnet.

D.    Changing magnetic flux induces a current through the tube that produces a magnetic field opposing this change.

Explanation / Answer

ans: D.    Changing magnetic flux induces a current through the tube that produces a magnetic field opposing this change.

When magnet is dropped , the conducting tube experiences change in magnetic field from falling magnet ,

therefore from Lenz law , this changing magnetic filed induces current in the tube .

The induced current create itselves a magnetic filed , this induced magnetic field opposes magnetic field from the magnet , hence the magnet falls slowly.

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