A loop of wire of radius a = 35 mm has an electrical resistance r = 0.036 ω . the loop is initially inside a uniform magnetic field of magnitude b0 = 1.5 t parallel to the loop's axis. the magnetic field is then reduced slowly at a constant rate, which induces a current i = 0.20 a in the loop. how long does it take for the magnitude of the uniform magnetic field to drop from 1.5 t to zero?