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Basic Electrical Circuits
Basic Circuit Diagram
In the above circuit an electrical reservoir (the battery) is connected via a cable to a
terminal on the controlling device (the switch) whose contacts are either open or closed.
The other terminal on the switch is connected via a cable to the consumer (the bulb),
and the other side of the bulb filament is connected to ground (earth) by another cable.
The ground point is usually a part of the frame or engine, to which the battery negative
terminal is also connected.
When the switch contacts are open (as shown in the diagram), the circuit is broken and
no current flows. When the switch contacts are closed, the circuit is made and current
flows from the battery positive terminal through the switch contacts and bulb filament to
ground. The frame completes the circuit to the battery negative terminal and the bulb
illuminates.
Although some circuits on the circuit diagram may at first seem more complicated, it will
generally be found that they can be broken down into sections which do not differ
greatly from the basic circuit above.
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