Auniform magnetic field is applied perpendicular to the plane of the disk. when superconducting coils are used to produce a large magnetic field, a homopolar generator can have a power output of several megawatts. such a generator is useful, for example, in purifying metals by electrolysis. if a voltage is applied to the output terminals of the generator, it runs in reverse as a homopolar motor capable of providing great torque, useful in ship propulsion. at work the next morning, your supervisor tells you that the homopolar generator under consideration will have a magnetic field of magnitude b = 0.885 t and the radius of the disk is r = 0.420 m. the desired emf to be generated with the device is e m f = 30.0 v. your supervisor asks you to determine the required angular speed of the disk to achieve this result (in rev/min).