A rectangular loop and a circular loop are moving out of a uniform magnetic field to a field-free re

Question

A rectangular loop and a circular loop are moving out of a uniform magnetic field to a field-free region with a constant velocity $v$. In which loop do you expect the induced emf to be constant during the passage out of the field region?

Professor PC Thomas Classes · Answer

The induced emf is constant for the rectangular loop because the rate of change of area (and thus flux) is constant ($l 	imes v$). For a circular loop, the rate of change of area varies as it exits.