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. For example (6 x 6) / (6 + 6) = 36 / 12 = 3 ohms.
- If there are more than two branches, take the inverse of the sum of the inverses of each branch resistance. For example 1 / ((1 / 6) + (1 / 6)) = 3 ohms.

Example Two: The resistance in the circuit shown below circuit must be less than 6 ohms. It is actually 3.43 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 / 3.5A = 3.43 ohms.
If there are only two parallel branches, divide the product (multiply) of the resistances by the sum (add) of the resistances. For example (8 x 6) / (8 + 6) = 48 / 14 = 3.43 ohms.
If there are more than two branches, take the inverse of the sum of the inverses of each branch resistance. For example 1 / ((1 / 8) + (1 / 6)) = 3.43 ohms.