The four wires should all be the same length so that the whirligig is perfectly balanced. The cork is then covered with tinfoil so that there will be an electrical connection between the four small wires and the needle forming the shaft.
The two wires A C and B D are connected together by a wire A B and a piece of flexible wire led to the Wimshurst machine. The opposite side of the Wimshurst machine is then grounded or touched with the hand. If the whirligig is laid on the wires A C and B D as shown in the illustration and it is perfectly balanced it will commence to revolve and roll along the wires just as soon as the Wimshurst machine is set in operation. It is the escape of the electricity from the points of the four wires on the whirligig which causes this.
Other interesting experiments in static electricity may be performed with the aid of a Wimshurst machine and the experimenter who is sufficiently interested to continue farther is referred to any good book on physics or some such volume as "The Boy Electrician".
CHAPTER II. CELLS AND BATTERIES.
Sources of Current. One of the chief difficulties of the average young experimenter is to secure a satisfactory source of current for operating his apparatus.
There are three means at his disposal and he may draw his electricity from
1. A power or lighting circuit;
2. A dynamo;
3. Batteries.
[Illustration: FIG. 26.—A Voltaic Cell. A Voltaic Cell consists of a
Strip of Copper and a Strip of Zinc immersed in a dilute solution of
Sulphuric Acid.]
Only those who are so fortunate as to live in a house wired for light and power service and supplied from the street mains, are likely to be able to utilize the first named. Those experimenters who live in towns where there are no commercial power wires or whose homes are not wired for such service will have to therefore depend upon a dynamo or a battery.
A dynamo is a very satisfactory source of current, provided some sort of power, such as a windmill, water motor or small engine is available for driving it. A hand dynamo is unsatisfactory for some purposes because the experimenter is usually unable to drive the dynamo and attend to other work at the same time.