Practice!

Sample Problem

A bar of length 2 cm slides along metal rails at a speed of 1 cm/s. The bar and rails are

in a magnetic field of 2 T, pointing out of the page. What is the induced emf in the bar and rails?

Solution

The induced emf from a bar of length l moving along rails at a speed v in a magnetic

field of magnitude B is given by the formula emf = vBl. Since we are given the values

 for v, B, and l, this is simply a matter of plugging numbers into a formula. Remember that we need to convert to units of meters:

emf = vBl =  (0.01 m/s)  (2 T)  (0.02 m)  = 4 × 10-4 V