Question

Find the induced emf inside a 100-turn coil that has a change in area of 0.2m^2 to 0.6 m^2 in 3E-3 seconds with a magnetic field of 8E-3 T inside the coil.

Answer 1

By the Faraday's law magnitude of The induced emf in a coil is equal to the negative of the rate of change of magnetic flux times the number of turns in the coil. It involves the interaction of charge with magnetic field.

So

Induced emf = -N ∆(B.A)/∆t

We have N = 100 turns , B = 8×10^(-3) T, ∆A = (0.6-0.2) m^{​​​​​​2} = ∆A = 0.4 m^{​​​​​​2} , ∆t = 3×10(-3) seconds

So

induced emf = - 100× 8×0.4× 10^(-3) / 3×10^(-3) = -106.7 V

Here negative sign It means that the current always flows in a way to oppose the change in flux

So induced emf is 106.7 volts