Hydrometer.—A hydrometer is used to test the electrolyte solution in the cells of storage batteries. It consists of a weighted float and a graduated stem, and as sulphuric acid is heavier than water, the specific gravity reading will be proportional to the amount of acid. The hydrometer thus measures the relative amount of acid in the electrolyte and consequently reveals the condition of the battery.
Ammeter.—An ammeter is an electrical instrument which indicates the amount of current that the generator is supplying to the storage battery, or the amount of current that the storage battery is supplying for ignition, lights and horn.
Circuit Breaker.—The circuit breaker is a device which prevents excessive discharging of the storage battery. All the current for lights is conducted through the circuit breaker (Delco system). Whenever an excessive current flows through the circuit breaker it intermittently opens the circuit causing a clicking sound. This will continue until the ground is removed or the switch is operated to open the circuit on the grounded wire. When the ground is removed the circuit is automatically restored, there being nothing to replace as is the case with fuses.
Switch.—A switch opens and closes the various circuits and is for the purpose of controlling the light, ignition, generator and storage battery circuits.
Generator.—See chapter on [electrical starting systems].
Regulation.—(Delco). On account of the various speeds at which the generator must operate it is necessary that the output be regulated so that sufficient current is obtained at the low engine speeds without excessive current at the higher speeds. The regulation in this case is what is known as the third brush excitation in which the current for magnetizing the frame is conducted through the auxiliary or third brush on the generator commutator. With this arrangement the natural function of the generator itself causes less current to flow through the shunt field winding at the higher engine speeds. This weakens the magnetic field in which the armature is rotating and decreases the output of the generator.
Contact-breaker.—See chapter on [Atwater Kent ignition systems].
Coil, nonvibrating.—See chapters on [Atwater Kent ignition systems] and [Philbrin electrical systems].
Distributors.—See chapters on [Magnetos] and [Atwater Kent ignition systems].