ABSTRACT
An alternating current (ac) is induced in a conductor rotating in a magnetic field. The value of the current and its direction of flow in the conductor depends upon the relative position of the conductor to the magnetic flux. During one revolution of the conductor the induced current will increase from zero to maximum value (positive), back to zero, then to maximum value in the opposite direction (negative) and, finally, back to zero again having completed one cycle. A graph plotted to show the variation of this current with time follows a standard sine wave. The number of cycles completed per second, each comprising one positive and one negative half cycle, is referred to as the frequency of the supply, measured in hertz (Hz). Mains electricity is supplied in the UK as ac at a nominal frequency of 50 Hz (50 cycles per second).
