Question

A magnet is placed into a coil. The induced EMF across the coil is 10mV. What would the EMF be if the coil was replaced by a coil with twice as many coils, and the passage of the magnet into the coil took twice as long?

Answer 1

According to faradays law, induced EMF= Ndf/dt, where N is number of coils, f is flux through each coil, t is time.

Let the initial number of coils be N. Also let the change in flux be f in time t.

So, initial induced EMF= 10 mV = N f /t................equation 1

Now, finally, number of turns = 2N. Also, change in fux is f in time 2*t.

So, final induced EMF=2N*f /(2*t) = N f /t

= 10 mV (using equation 1).

So, new induced EMF= 10 mV.