Parallel Circuit Calculation Examples

Parallel circuit calculations can be quite complex, even for experienced electricians. Knowing how to calculate the current and resistance of a given circuit is essential for anyone who wants to work with electricity. By understanding how resistors interact with each other in a parallel circuit, it’s also possible to build efficient, effective electrical systems. Here, we’ll explain the basics of parallel circuit calculations and provide a few examples.

Understanding Parallel Circuits

Parallel circuits are series of components that are connected side-by-side, so that each component is on its own branch. This kind of circuit allows electricity to move along multiple paths at once, which makes the circuit much more powerful than a simple series circuit. A parallel circuit is also less prone to short circuits, because current flows in multiple directions simultaneously, so if one path is blocked, current can still flow through the others.

Calculating Parallel Circuit Resistance

Calculating resistance in a parallel circuit is slightly different than in a series circuit. To find the total resistance of a parallel circuit, you need to use this equation:

1/Rtotal = 1/R1 + 1/R2 + 1/R3 + ....

This equation essentially sums up all of the individual resistances in the circuit, then finds the inverse of the total. As an example, let’s say we have a parallel circuit with three resistors: one with a resistance of 4 ohms, one with a resistance of 8 ohms, and one with a resistance of 12 ohms. Using the equation above, we would get:

1/Rtotal = 1/4 + 1/8 + 1/12

Which simplifies down to:

Rtotal = 3 ohms

Calculating Parallel Circuit Current

The total current in a parallel circuit is equal to the sum of all of the individual currents in each branch. The individual branch currents can be found using Ohm’s Law: I = V/R, where V is the voltage across the resistor, and R is the resistance of the resistor.

Let’s look back at our example circuit with three resistors. We know the total voltage is 24 volts, and the resistances of the three resistors are 4 ohms, 8 ohms, and 12 ohms. To find the total current, we need to find the individual branch currents first.

For the 4 ohm resistor, I = 24/4, or 6 amps.

For the 8 ohm resistor, I = 24/8, or 3 amps.

For the 12 ohm resistor, I = 24/12, or 2 amps.

The total current in the circuit is therefore 6 + 3 + 2 = 11 amps.

Conclusion

Parallel circuits have many advantages over series circuits, but they can be tricky to calculate. With some practice, however, electricians can master the equations needed to calculate the current and resistance of a parallel circuit.