Parallel Circuit Calculator
Find the current in each branch of a parallel circuit, and the total current from the supply. Enter the voltage and up to three resistors. Change any value and the answer follows.
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How it works
In a parallel circuit, each branch gets the full supply voltage. Each branch current is the voltage divided by that branch's resistance.
The total current is the sum of the branch currents. The equivalent resistance is one divided by the sum of one divided by each resistance, and it equals the voltage divided by the total current.
Worked example
With 12 volts across branches of 4, 6 and 12 ohms, the total current is 6 amps, and the equivalent resistance is 2 ohms.
Questions
Why does the total current equal the sum of the branches?
Current splits between the branches, and the pieces join back together at the supply. Nothing is lost on the way, so the parts add up to the whole.
Does this work for AC circuits?
Not fully. It handles resistors on a steady voltage. Circuits with capacitors or coils need impedance, which this does not use.
Why is the equivalent resistance smaller than any one resistor?
Each extra branch gives the current another path, so the combined resistance drops below the smallest branch.
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