disc 105 magnetic forces are exerted on the moving charges the moving charges in turn exert the force to the disc 105 thereby causing the disc 105 to rotate and store kinetic energy when the voltage source is replaced with an electrical load the kinetic energy stored in the rotating disc 105 can be used to generate electricity as the conductive disc 105 rotates within the magnetic field an electromotive force emf is induced in the disc 105 thereby causing current flow through the load the amount of voltage v t that is generated by the mehg 105 is approximately given by the formula v t u03c9 m ue89e b ue8a0 r 2 2 r 1 2 2 where u03c9 m is angular velocity of disc b is the flux density of the magnetic field that is perpendicular to the motor r 1 is the radial distance between the center of the disc 105 and the first contact brush 215 and r 2 is the radial distance between the center of the disc 105 and the second contact brush 220 further the impedance z of the mehg is given by the formula z _ b 2 2 ue89e u03c0 ue89e ue89e t ue89e ue89e u03c1 ue89e 1 j ue89e u03c9 ue89e and the equivalent capacitance c is given by c 2 ue89e u03c0 ue89e ue89e t ue89e.