Shunt-wound Field.—Fig. [32] represents what is known as a "shunt-wound" dynamo. Here the[p. 48] field wires (H, H) connect with the opposite brushes of the armature, and the wires (I, I') are also connected with the brushes, these two wires being provided to perform the work required. This is a more useful form of winding for electroplating purposes.
Compound-wound Field.—Fig. [33] is a diagram of a "compound-wound" dynamo. The regular field winding (J) has its opposite ends connected directly with the armature brushes. There is also a winding, of a comparatively few turns, of a thicker wire, one terminal (K) of which is connected with one of the brushes and the other terminal (K') forms one side of the lighting circuit. A wire (L) connects with the other armature brush to form a complete lighting circuit.
CHAPTER V[ToC]
HOW TO DETECT AND MEASURE ELECTRICITY
Measuring Instruments.—The production of an electric current would not be of much value unless we had some way by which we might detect and measure it. The pound weight, the foot rule and the quart measure are very simple devices, but without them very little business could be done. There must be a standard of measurement in electricity as well as in dealing with iron or vegetables or fabrics.
As electricity cannot be seen by the human eye, some mechanism must be made which will reveal its movements.