A time-dependent magnetic field →B(t) is produced in a cylindrical region of radius R. The magnetic field is given as →B(t)=B0t^z for 0≤r<R and zero for r > R, where B0 is a positive constant, ^r is the unit vector in the radially outward direction and ^θ is the unit vector in the tangential direction, such that ^r×^θ=^z. The electric field at r> R is