The magnitude of the magnetic field in a magnetic resonance imaging (MRI) machine can be as great as B = 2.0T . Under normal circumstances, this field cannot be shut off by just flipping a switch. Instead the magnitude needs to be carefully decreased to zero. In an emergency, however, the magnet can be "quenched" so that B reduces to zero in 20 s. Such a quench can cost thousands of dollars and likely damages the magnets. Assume that the magnetic field exists inside a cylinder of radius R = 400mm and length ? = 500mm .

How much magnetic potential energy is dissipated when the magnetic field is quenched in this way?

What is the average rate at which energy is dissipated?