What is positive and what negative electricity?
No difference in electricity in itself. When a body has more than its natural amount of electricity, it is said to be charged positively; when it has less than its natural amount it is negatively charged.
What is a Cell; what a Battery?
If a piece of zinc and copper joined by a wire be dipped in a liquid—generally weak sulphuric acid—which will act chemically on the metals, a current is produced. Such an arrangement is called a couple, or cell. If many cells are connected, then it is called a battery.
What is Thermo-electricity?
If two bars of any unlike metal—for example, antimony and bismuth—be soldered together at one end, and the other ends be connected by a wire and then the soldered end heated, a current will flow.
What effects are produced by currents?
They produce heat, light, decomposition and combination in liquid chemical compounds; they melt all metals, excite magnetism, and in the animal body excite movements of the muscles.
Can you specify these effects?
A strong battery produces heat in such a degree that all metals can be melted. Light is produced in flashes, or if the end of the leading wires are connected with two pencils of hard carbon, and brought very near together, then a brilliant light, or arc, called the voltaic arc, is produced. This is the dazzling bright light which we call electric light. The chemical effect of a current in decomposing compound substances is called electrolysis. In this way water can be decomposed into its compounds, hydrogen and oxygen; copper sulphate into sulphur and metallic copper, etc. In this way we can deposit strong adherent films of metal on the surface of any conductor; for if the article to be coated be attached to the negative electrode of a battery, and dipped into a solution of the metal with which we desire to coat the article, say copper or silver, and the positive electrode be attached to a plate of copper and also dipped into a liquid, when the current passes, the metal will be decomposed and deposited in a uniform layer over the article at the negative electrode. This process is called electro-plating.