Parallel Resistors

Parallel resistors are resistors connected in a way that the current can take more than one path. You can see an example of resistors connected in parallel in figure 1.

Image of a closed circuit. The circuit has a rectangle shape, with a line dividing it almost in the middle. On the inferior base, there is the battery with its negative and positive poles labeled V zero. On the line dividing the rectangle, to the right of the battery, there is one resistor labeled R1, drawn as a zigzag line. On the right side of the rectangle, even further to the right from the battery and R1, there is a second resistor also drawn as a zigzag line labeled R 2.

Figure 1. Resistors connected in parallel.

In resistors connected in parallel the charge and energy are preserved (as in any other circuit). Current and Voltage behave differently in parallel resistors when compared to series resistors. Let's use figure 1 as an example.


Current (Amperes), refer to the number of electrons that are passing through a certain point of the circuit in a given time (Coulombs per second). If the electricity can take more than one path, that means that the current will split between the different possible paths (R1 and R2). The intensity of current that will go through each path will depend on Ohm's Law. The path with the lowest resistance will receive more current.


Voltage behaves differently in resistors connected in parallel. Voltage is the energy contained per Coulomb of charge, so when the electricity splits between R1 and R2 the current splits, but the energy that each of the Coulombs is carrying is the same

For example, if the battery is providing 12 volts both R1 and R2 will receive 12 volts each, while the current will be split between them.

Equivalent Resistor

An equivalent resistor is a resistor that will have the same effect on the circuit than the resistors already in the circuit (R1 + R2 in this case). In parallel resistors calculate the equivalent resistor is a bit more complex than in series resistors. In order to be able to calculate the resistor, you would need to follow the next formula.

1/RT = 1/R1 + 1/R2 one divided by the equivalent resistance R T is equal to the sum of one divided by the resistance in resistor 1 R 1 and one divided by the resistance in resistor 2 R 2

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