Before taking up the study of automobile ignition systems and electrical appliances, we will first devote a little time to study, in order to become familiar with the different electrical parts, functions, terms and names applied to the various units, and machines.

In the first place electricity is not a juice or fluid that flows through a wire, but is a generated electro-motive force that may be held in storage or conducted from one place to another. It will not flow without a round circuit and seeks ground return at the slightest opportunity. It is designated in terms which express quality, quantity, force and action.

Voltage.—A volt is an electrical unit, expressing the force or pressure of the current. The voltage of a system simply means the difference of pressure exerted on the system measured in volts.

Ampere.—An ampere is an electrical unit expressing the quality or intensity of the current.

Ohm.—An ohm is an electrical unit expressing resistance; or the resistance of conductors to the flow of current.

Current.—The current is the generated electro-motive force.

Circuit.—Electricity will not flow unless there is a circuit or ground return to its original source.

Low Tension Current.—Low tension current is generated in the primary winding or coil by placing it in a magnetic field. It will flow from one point to another but has very little strength and will not jump the gap at the spark plug. It is used for lighting purposes, or conducted to an induction coil which transforms it into a high tension alternating current.

High Tension Current.—High tension current is generated in the secondary coil by interruption of the primary current or by the rapid magnetization and demagnetization of the core and primary coil.

Direct Current.—Direct current is produced by placing a coil or wire in a magnetic field. It is usually conducted to an induction coil where it is transformed into a high tension alternating current.

Alternating Currents.—Alternating currents are produced by the rapid breaking down and building up of the primary current. An alternating current flows forward from zero to its highest point of strength and back again to zero. The alternating action takes place so rapidly that a light can be connected in this circuit and it will burn steadily without any noticeable fluctuation.

Induction Coil.—An induction coil consists of a soft iron core; a primary and secondary winding, and a set of platinum points. The primary winding is wound directly over the core and consists of a few turns of thick wire. The secondary wire is wound over the primary and consists of a great many turns of thin wire. Fig. 54 shows the functional action of an induction coil. Both of the coils are wound on the soft iron core A-B. The primary current which is supplied in this case by a cell or number of cells, C and D, is broken at frequent intervals of time. The method of doing this is as follows: One terminal of the primary coil is connected to the fixed platinum stud D, the other terminal to a spring which carries a piece of soft iron, E. When the spring is unbent it touches the stud D, and a current passes in the primary. The core of soft iron becomes magnetized and attracts the soft iron disc, E, thus breaking contact at D. The current is stopped and the core immediately becomes unmagnetized, the spring flies back and the contact is again made. The process is then repeated. When the contact in the primary is broken the current flows in one direction in the secondary coil, when it is made the current flows in the opposite direction in the secondary. Thus an alternating current is set up in the secondary current of great frequency.

Commutator.—The commutator or timer as it is commonly called is used only in connection with the induction coil to complete the circuit when a spark is required at the plug in the cylinder.

Insulation.—Insulating is the act of covering a conductor with a non-conducting substance to prevent the spark from jumping or seeking ground.

Choking Coil.—A choking coil in simple form consists of a coil and iron core to increase self-induction. It is used to reduce currents of high pressure and is commonly called a bucking coil.

Fuse.—A fuse is used to prevent conductors or coils from being damaged by heat generated from high pressure currents. It consists of a metal and glass tube which contains a fine wire. This wire being much thinner than the wire of the cable, the heat naturally develops faster at this point, and is soon high enough to melt the wire and break or open the circuit, and thus any further damage to the insulation is prevented.

Condenser.—A condenser usually consists of a few strips of folded tin foil insulated from each other with paraffined or oiled paper. It absorbs, restricts and distributes high pressure currents and also prevents excessive sparking at the contact points.

Dynamo.—A dynamo is a machine which converts mechanical energy into electric energy, and must consist of at least two separate parts; the field magnets to create the magnetic field, and the armature or conductor in which the current is generated. One or the other of these must be in motion in order to cut the lines of magnetic force crossing the field. Fig. 55 shows the operation of the most common or simplest type of alternating current producing machine, which is similar and conforms in action to the high tension magneto and generator. Field pieces magnetize the pole pieces N and S. A wire coil is placed in the field at right angles to the magnetic lines of force turned to the right. It takes up the position of the dotted lines and no lines of force are cut, whereas in its original position, as many lines of force as possible are cut. Turning the coil on its axles, a-b, causes the lines of force cut by c-d, and e-f to vary from the highest number of lines that it is possible to cut to zero and back again, thus constantly changing the flowing direction of the current. The reversal of the current takes place at the instant that the coil passes the point where it cuts the greatest number of lines of force. The ends of the coil are connected to a commutator on the shaft a, b. Steel insulated brushes pick the current from the commutator ring and conduct it to the brush post; an insulated wire conductor is attached to this post and conducts the current to the place of use or storage.

Voltaic Cell.—The source of energy of a voltaic cell is the chemical action. (See accumulator).

Accumulator.—The standard accumulator or storage battery is composed of three cells or hard rubber jars in which a number of lead plates are immersed in a solution of sulphuric acid and water known as electrolyte. The plates are stiff lead grids which hold a paste made of various oxides of lead. Six plates in each cell are joined to the positive terminal, and seven plates in each cell are joined to the negative terminal. Thin wooden separators are inserted between the plates to prevent them from touching one another. In the forming process the material on the positive plates becomes converted into brown peroxide of lead; the negative plates assume the form of gray metallic lead. The material on both plates is known as active material. When current is taken from the cells the sulphuric acid in the electrolyte combines with the active material of the plates to form sulphate of lead, and when the battery is recharged the lead sulphate is again converted into the original active material and the acid set free in the solution.

Storage Battery.—For construction and action see Accumulator. For care see chapter on storage batteries.

Electrolyte.—A chemical solution used in voltaic cells consisting of two parts sulphuric acid added to five to seven parts of water by volume.

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.