=Resin.= A solid inflammable substance or gum, and a good non-conductor in electrical work. It is the product obtained by distilling the sap of the pitch-pine. The name is also applied to the product of distilling the sap of other trees. Common resin, shellac, lac, Dragon’s-blood, and other substances of a similar nature are resins. They are all dielectrics, and the source of negative frictional electricity when rubbed with cotton, wool, flannel, silk, or fur. =Resistance.= That quality of an electric conductor in virtue of which it opposes the passage of an electric current, causing the disappearance or modification of electro-motive force, and converting electric energy into heat energy. =Resistance-box.= A box filled with resistance-coils connected in series and provided with a switch, so that any number of the coils may be cut out. =Resistance, Carbon.= A resistance composed of carbon as a substitute for a coil of wire. Carbon rods are placed close together having an air space between them, with alternate ends connected. Piles may be built up of carbon plates, whose resistance is made to vary by changing the pressure. =Resistance-coil.= A coil of wire metal or other substances having the power to resist a current of electricity. A coil of wire used to measure an unknown resistance by virtue of its own known resistance. (_See also_ Coil, Resistance.) =Resistance, Dielectric.= (_See_ Dielectric Resistance.) =Resistance, Electrolytic.= The resistance of an electrolyte to the passage of a current decomposing it. It is almost entirely due to electrolysis, and is intensified by counter-electro-motive force. When a current of a voltage so low as not to decompose an electrolyte is passed through the latter, the resistance appears very high and sometimes almost infinite. If the voltage is increased until the electrolyte is decomposed the resistance suddenly drops to a point lower than the true resistance. =Resistance, Internal.= The resistance of a battery, or generator, in an electric circuit as distinguished from the resistance of the rest of the circuit. =Resistance, Liquid.= A liquid of varying specific gravity used to create resistance to the passage of the electric current. Resistance effected by the use of liquid through which a current must pass to complete a circuit. =Resistance, Metallic.= The resistance of metals to the electric current. German-silver resistance as distinguished from that of water, carbon, or other substances. =Resistance, Ohmic.= True resistance measured in ohms as distinguished from counter electro-motive force. (_See also_ Ohmic Resistance.) =Resistance, Spurious.= The counter-electro-motive force. In its effect of opposing a current and in resisting its formation it differs from true resistance. True resistance diminishes current strength, absorbs energy, and develops heat. Spurious resistance opposes and diminishes a current without absorption of energy or production of heat.