The simple alternator

 If a loop of wire is rotated between the poles of a magnet as shown in Fig. 2.1 , the loop of wire will cut the lines
of magnetic fl ux which pass from the north to the south pole. This fl ux cutting causes a voltage to be induced
in the loop of wire.
 If this induced voltage is collected by carbon brushes at the slip rings and displayed on a meter or CRO, it will
be seen to induce fi rst a positive and then a negative voltage. We call this changing voltage, an alternating
voltage and the shape that it follows is called, in mathematics, sinusoidal.