Arectangular loop of area a is placed in a region where the magnetic field is perpendicular to the plane of the loop. the magnitude of the field is allowed to vary in time according to b = bmax e-t/τ , where bmax and τ are constants. the field has the constant value bmax for t < 0. find the emf induced in the loop as a function of time. (use the following as necessary: a, bmax, t, and τ.) g