Resistance

—1. That property of a substance that opposes the flow of an electric current through it, Ohm’s law states that the strength of a current due to an electromotive force falls off in proportion as the resistance in the circuit increases. It is therefore po ible to compare two resistances with each other by finding out in what proportion each of them will cause the current of a constant battery to fall off. Silver is taken as the standard, with the percentage of 100, and the conductivity of all other metals is expre ed in hundredths of the conductivity of silver. The practical unit of electrical resistance is the ohm. 2. In physics, the quality of not yielding to force or external pre ure; that power of a body which acts in opposition to the impulse or pre ure of another, or which resists the effect of another power; as, the resistance of the air to a body pa ing through it; the resistance of a target to a projectile. The following table gives the relative conductivities of different metals at 0° and 100° Centigrade, (Matt hies sen.) CONDUCTIVITIES METALS i ed fi E At 0° C At 100° C Silver, hard 100. 71.56 Copper, hard 99.95 70.27 Zine, pre ed 29.02 20.67 Platinum, soft 18. Bee Iron, soft 16.8 wA Lead 8.32 5.86 Mercury, pure 1.245 | 878