A wire loop of radius 0.40 m lies so that an external magnetic field of magnitude 0.30 T is perpendicular to the loop. The field reverses its direction, and its magnitude changes to 0.20 T in 2.5 s. Find the magnitude of the average induced emf in the loop during this time.

The magnitude of the average induced emf in the loop is 0.1 volts.

Explanation:

let Ф be the flux in the loop, B be the magnetic field and A be the area of the loop.

the induced emf in the loop is given by:

ε = - dФ/dt

= - d (B*A) / dt

= - A*d (B) / dt

= - π*r^2*d (B) / dt

= - π * (0.40) ^2 * (0.20 - (-0.30)) / (2.5 - 0)

= 0.1 volt

Therefore, the magnitude of the average induced emf in the loop is 0.1 volts.