Question

A classic demonstration illustrating eddy currents is performed by dropping a permanent magnet inside a conducting cylinder. The magnet does not go into free fall. Instead it reaches terminal velocity and can take a few seconds to drop a length of about a meter. Suppose the mass of the magnet is 70 g and width of 1.0 cm. It falls with a terminal velocity of 10 cm/s and the length of the pipe is 80 cm. The magnitude of the Joule heating from the eddy currents is approximately:________

Answer 1

Answer:

The correct solution is "0.69 N".

Explanation:

The given values are:

Mass of magnet,

m = 70 g

or,

   = 0.07 kg

Width,

= 1.0 cm

Velocity,

= 10 cm/s

Length of the pipe,

= 80 cm

Whenever the velocity is constant, then the net force which is acting on the magnet will be "0".

On the magnet,

The up-ward force will be:

⇒  $F=mg$

On substituting the values, we get

⇒      $=0.07\times 9.8$

⇒      $=0.69 \ N$