Figure 1-12.- Typical automotive circuit.

automobile body is called grounding. The majority of equipment you will encounter in the NCF will have an electrical system with a negative ground. Vehicles with positive ground are very uncommon, but it is always good practice to note what type of grounding system is used on the equipment you are working on.

Series circuits (fig. 1-13, view A). A series circuit consists of two or more electrical components connected in such a manner that current will flow through all the components. Important characteristics of a series circuit are as follows:

Any break in the circuit (such as a burned-out light bulb) will render' the entire circuit inoperative.

Current (amperage) will be constant throughout the circuit.

Total resistance of the circuit is equal to the sum of each individual resistance.

Total voltage of the circuit is equal to the sum of the individual voltage drops across each component.

Parallel circuits (fig. 1-13, view B). A parallel circuit consists of two or more electrically operated components connected by parallel wires. In a parallel circuit, the current divides, part of it flowing into one component and part into the others. Practically the same voltage is applied to each component, and each component can be turned on or off independently of the others. Important characteristics of parallel circuits are as follows:

The total resistance of the circuit will always be less than the resistance of any individual component.

The disconnection or burning out of any individual component in the circuit will not affect the operation of the others.

The current will divide itself among the circuit branches according to the resistance of the individual devices. The sum of the individual amperages will be equal to the total circuit current.

The voltage will be constant throughout the circuit when measured across the individual branches.

Series-parallel circuits (fig. 1-13, view C). The series-parallel circuit is a combination of the two configurations. There must be at least three resistance units to have a series-parallel circuit. Important characteristics of series-parallel circuits are as follows:

The total circuit voltage will be equal to the sum of the total parallel circuit voltage drop plus the voltage drop of the individual series circuit component.

The total circuit resistance will be equal to the sum of the total parallel circuit resistance plus the individual resistance of the series circuit components.

Figure 1-13.- Circuit configurations.

Current flow through the total parallel circuit will be equal to the current flow through any individual series circuit component.

The disconnection or the burning out of the series components will completely disable the entire circuit, whereas a failure of any of the parallel circuit components will leave the balance of the circuit still functioning.

Short circuit (fig. 1-14, view B). A short circuit occurs when copper touches copper, such as when wiring insulation between two wires fails and the wiring makes contact.