A magnet is dropped down an infinitely long vertical copper tube

Options

A. the magnet moves with continuously increasing velocity and ultimately acquires a constant terminal velocity
B. the magnet moves with continuously decreasing velocity and ultimately comes to rest
C. the magnet moves with continuously increasing velocity but constatnt accleration
D. the magnet moves with continuously increasing velocity and acceleration

Answer

A

Explanation

If bar magnet is falling vertically through the hollow region of long vertical copper tube (due to 'non-uniform' magnetic field of magnet) change and eddy currents are genrated in the body of the tube by Lenz's law the eddy current opposes the falling of the magnet which therefore experience a retarding fore. the retarding force increase with increasing velocity of the magnet. the magnet then attains a constant final terminal velocity i.e., magnet unlimately falls with zero acceleration in the tube.