The magnetic field inside a long solenoid is given by B mu0

The magnetic field inside a long solenoid is given by B = mu_0nI(t) z, where n is the number of turns of wire per unit length, and I(t) is a time-changing current. Because the magnetic field changes with time, there is an induced electric field. Find this electric field, both inside and outside the solenoid.

Solution

V = -nl*d(BA)/dt = -n²l²mu₀dI/dt
Use the standard formula it will be same both inside and outside