Storage Cells
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
p-376
2025-12-11
24
If a galvanometer is coupled to the terminals of a voltameter after a current has been sent through it, the needle will be deflected, showing that the voltameter is itself capable of giving out a current.
Demonstrations. - Fasten two sheets of lead to the opposite sides of a wooden support and suspend them in a jar of dilute sulphuric acid. Connect the cathode of two or three dry cells coupled in series, to one of the plates and the anode to one terminal of a double snap switch. Couple an electric bell to the plate and switch as shown in Fig. 1. Send the current from the battery through the cell for a short time - a second or two will answer - then snap the switch, the battery will be cut out, the bell will be thrown in circuit with the cell and will begin to ring. The action will be strong at first and gradually die out.
Repeat and note the effect of the length of time the battery is sending a current upon the length of time the bell will ring.
Repeat, using a 2-volt, 1-candle power incandescent lamp instead of the bell.
It will be observed that there is a vigorous production of oxygen from the anode and of hydrogen from the cathode of the lead-sulphuric acid cell. The oxygen combines with the lead of the anode forming lead peroxide (PbO2) which covers the plate a chocolate brown. When the bell is put in the circuit, the current passes through the cell in the opposite direction and the lead peroxide on the anode is changed to a spongy form of lead. Plante was the first to discover this effect and devised this form of battery for the storing of electrical energy. In recent forms of this battery the lead plates, or grids, are grooved in such a way that the grooves can be filled with a paste of red oxide of lead for the positive electrode and litharge for the negative.
There are many types of storage cells in practical use. Figure 2 shows the positive and Fig. 3 the negative electrode of the chloride accumulator cell, and Fig. 4 shows one of the smaller cells ready for use. The large size of the plates reduces the internal resistance of the cell and makes a heavy current possible.
Storage batteries are used as the motive power in electric automobiles and trucks. An efficient type is the Edison cell (Fig. 5), in which the liquid used is a solution of caustic potash and the electrodes are nickel hydrate and iron oxide, the nickel being the positive electrode and the iron the negative. The containing cans (Fig. 6) are made of corrugated sheet steel which secures the cells against breakage.
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