# How to Calculate the Amps and Resistance of a Parallel Circuit ••• circuit board image by Gale Distler from Fotolia.com

According to the Princeton University WordNet, a circuit is an electrical device that provides an avenue through which current can move. Electrical current is measured in amperes, or amps. The number of amps of current flowing through the circuit may change if the current crosses a resistor, which impedes current flow. In a series circuit, the current lessens with each resistor it crosses. In a parallel circuit, the resistors are placed in such a way that they are all receiving the same amount of current. Current and resistance can be calculated using Ohm's law.

## Rtotal Method

Calculate the total resistance of the parallel circuit by using the equation 1/Rtotal = 1/R1 + 1/R2 + 1/R3 + ... + 1/Rn. This equation states that by adding the inverses of all of the individual resistors, you will get the inverse of the total resistance. Pretend that you have two resistors in parallel, and each is four ohms. Rtotal equals 2 ohms.

Identify the voltage of the system. Add the voltages together if two power sources in series are being used.

Divide the voltage by Rtotal to determine the final value of current after it passes through the parallel resistors. This is Ohm's law, which can be written as I = V/Rtotal.