current is perpetually flowing one way through the circuit. The effect of the commutator is, in fact, equivalent to transposing the brushes of the collecting rings of the alternator every time the coil reaches a zero position.
Figs. 71 and 72 give end views in section of the coil and the commutator, with the coil in the position of minimum and maximum efficiency. The arrow denotes the direction of movement; the double dotted lines the commutator end of the revolving coil.
PRACTICAL CONTINUOUS-CURRENT DYNAMOS.
The electrical output of our simple dynamo would be increased if, instead of a single turn of wire, we used a coil of many turns. A further improvement would result from mounting on the shaft, inside the coil, a core or drum of iron, to entice the lines of force within reach of the revolving coil. It is evident that any lines which pass