Application: Homopolar generator. A disk of radius 100 mm rotates in a uniform sinusoidal magnetic field at 6000 rpm as shown in Figure 10.45. The frequency of the ac field is 400 Hz and its amplitude is 0.1 T. A wire is connected to the center of the disk and one is sliding on its edge, making good contact. What is the voltage (emf) between points A and B?