Power (P).—The rate of doing work. When an ampère passes through an ohm, the unit power, called a watt, is required.
Quantity (Q).—The Unit is the Coulomb.
Relay.—An electro-magnet which, receiving its current from a distance, closes the circuit of a local battery so as to produce the required effect of strength.
Resistance (R).—The opposition presented by the circuit to the development of the current. The Unit of resistance is the Ohm.
Rheostat.—An instrument for inserting resistances. A valuable artificial resistance employed for measuring unknown resistances.
Return Current.—The current in the wire leading to the machine.
Rigger.—The pulley or wheel by which power is transmitted.
Secondary Battery.—Wrongly termed an accumulator, is an appliance for storing energy in such a form that it shall be available for the reproduction of electric currents.
Secondary Generator.—A transformer of a current of high potential into a current of less E. M. F.
Series.—The plan of connecting lamps so that the current passes one after the other.