Parallel Circuits
Parallel circuits are commonly used in automotive lighting circuits.
A parallel circuit has several unique
characteristics:
There is more than one path for electric current.
The total amount of electric current is equal to the sum of the individual branch currents.
The source voltage will be dropped across all of the electrical loads in each branch of the circuit.
There can be more than one load in each branch.
An open anywhere in a branch will stop the current in that branch, but leave the other branch
unaffected.
The total circuit resistance is less than the resistance of the resistive loads of any single branch.
Example One: The resistance in the circuit shown below circuit must be less than 6 ohms.
It is
actually 3 ohms.
There are several ways of calculating the resistance in a parallel circuit:
The easiest way is to divide the voltage by the total current, 12V / 4A = 3 ohms.
If there are only two parallel branches, divide the product (multiply) of the resistances by the
sum (add) of the resistances.
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 Winter '12
 JohnKelly
 Ohms, Resistor, Electrical resistance, Parallel Circuits

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