Fig. 2.
2. Carbon-Zinc Cell. Fig. 2. In case you want to make your cell out of carbon and zinc rods, and do not have any means of making holes for them in the wood, as in [App. 3] and [4], you will find this method useful. Cut grooves, G, into one side of the wood, A, which should be about 4½ × 1 × ½ in. The grooves should be quite deep, and so placed that the rods will be about ¼ in. apart. A strip of tin, T, ½ in. wide, should be bent around each rod. The screw, S, put through the two thicknesses of tin will hold the rod in place. Another screw, X, acts as a binding-post. The zinc rod only is shown in Fig. 2. The carbon rod is arranged in the same way. Use the fluid of [App. 15].
3. Note. When the bichromate solution of [App. 15] is used for cells, the strong current is given, among other reasons, because the zinc is rapidly eaten up. This action goes on even when the circuit is broken, so always remove and wash the zinc as soon as you have finished.
4. Carbon-Zinc Cell. Fig. 3. The wooden cross-piece, A, is 4½ × 1 × ½ in. The carbon and zinc rods, C and Z, are 4 in. long × ½ in. in diameter. The holes are bored, if you have a brace and bit, so that they are ¾ in. apart, center to center. This makes the rods ¼ in. apart. To make connections between the rods and outside wires, cut a shallow slot at the front side of each hole, so that you can put a narrow strip of tin or copper, B, in the hole by the side of each rod. Setscrews, S, screwed in the side of A, will hold the rods in place, and at the same time press the strips, B, against them. Connections can easily be made between wire and B by using a spring binding-post, D, or by fastening the wire direct to the strips, as shown in [App. 4].
Fig. 3.
Use the battery fluid given in [App. 15], and use a tumbler for the battery jar. This cell will run small, well-made motors, induction coils, etc. ([See § 3].)