Components in parallel use up the same amount of voltage.

Recall the every component, such as resistors in circuit, change the energy of the charge carriers that travel through the circuit. Below is a series circuit illustrating this concept.

The video below shows how to identify resistors that are in parallel, how to calculate the equivalent, or total, resistance, and how to redraw a circuit when combining resistors in parallel.

The above video is linked from YouTube, Here is the link, http://www.youtube.com/watch?v=-XVpemSSluQ

The equation for adding resistors in parallel is,

Where R_e is the equivalent resistance of the parallel combination. R₁, R₂,... R_n are the resistors themselves. The most common error when calculating the equivalent resistance for parallel resistors is forgetting to inverse the summation.

Resistors, or any electrical component, in parallel all drop the same potential difference. In other words everything that make a parallel combination of resistors use up the same amount of voltage. This is because all the resistors in parallel are attached to the same two on both sides of the resistors. Since the wires on opposite sides of the resistors have different voltages, each resistor must use drop the same amount of voltage as the charge travels from on wire, through the resistors, to the other wire.

Example

What is the equivalent resistance when a 4 Ω resistor is in parallel with a 12 Ω resistor.

Solution