Lesson 1/Learning Event 2
FIGURE 14. SERIES-PARALLEL CIRCUIT.
The SERIES-PARALLEL circuit is a combined series and parallel circuit. This is illustrated by the
three-bulb circuit here. All the current flowing in the circuit must go through bulb 1. There is only
one path here so this is the series part of the circuit. But, on the other side of bulb 1, the electrical
path divides. There, part of the current flows through bulb 2 and the remainder through bulb 3.
Then, the paths join again to form a single path to the power source. The divided paths through
bulbs 2 and 3 are the parallel part of the circuit.
ELECTRICAL CIRCUIT DEFECTS
Circuits are also described as being grounded, shorted, or open or as having a high-resistance
connection. These terms refer to conditions that exist in a circuit and usually describe a defect.
Let's go into these terms in more detail so you will grasp the full meaning of each.
A GROUNDED circuit exists when defective insulation allows a conductor, such as a wire, to touch
the vehicle frame. This probably causes most of the electrical fires on automotive vehicles.