Fig. 5.—Tray to carry battery of cells.
Fig. 6.—The complete battery.
The eight components of the battery being thus complete, nothing necessary remains but to connect them together. However, they will prove more portable and self contained if arranged in a shallow wood tray. This may be either a confectionery box—if one of suitable dimensions is obtainable—or can perhaps be constructed as indicated by the accompanying sketch, with handles at either end ([Fig. 5]). It should certainly be strong, as the set of jars is of considerable weight, and would, if accidentally dropped, create a pretty printers’ pi. Lastly, when the cells have been arranged in two rows of four a side, the finishing touch is to join the copper wire ends by twisting, according to the plan shown in [Fig. 6], and the battery is complete. The end wires A and B will be referred to hereafter as negative and positive terminals respectively.
Fig. 7.—The compass test.
Experiment 1.—Connect one extremity of a straight wire with the battery’s positive terminal, and place it on the table so as to lie due north and south. Above it stand a compass, whose needle—also pointing due north and south—will be parallel to the wire ([Fig. 7]). Now, when the free end of the north-south conductor is connected to the battery’s other terminal so that a current may flow, the needle swings round at right angles and thus now lies east and west. Needless to add, electricity prompts the needle’s behavior, and unless such movement does take place, the cells are at fault somewhere.
Fig. 8.—Spark-producing.
Experiment 2.—Having decided by the compass’s behavior that the battery is actually efficient, bring the terminal wires into contact in the dark, and notice the slight spark ([Fig. 8]). Next obtain a spare bobbin from an old electric bell ([Fig. 9]), and pass the current round the coils whilst making the spark. This should now be more distinct—thicker, and brighter, though not so frequent—owing to induction taking place between the wire coils.