Ohm.—The Unit of resistance. A volt divided by an ampère.
Ohm’s Laws.—Laws, investigated by Ohm, regulating electrical current magnitudes. Calling the current C, electro-motive force E, and resistance R: the expression is
| Current | E. M. F. | Resistance. |
|---|---|---|
| C = E ⁄ R, amps. | E = C × R, volts. | R = E ⁄ C, ohms. |
| ([See Electrical Measurements].) | ||
Osmose.—The process of diffusion of liquids through a porous division.
Paraffin.—An insulating substance much used in telegraphic work.
Plummer Block.—The bearing on which a shaft revolves.
Polarity.—The distinct features of the two separate poles of a magnet.
Poles.—The two ends of a magnet. The wires, plates, &c., leading from a battery.
Positive.—In a machine the wire proceeding to the lamp. In a battery the zinc plate. Sign +.
Potential.—A word used to indicate a condition for work. Difference of potential is a difference of electrical condition. Potential of a battery means its E. M. F.