How to Calculate Resistors in Series and Parallel

Resistors in Series

When resistors are connected one after each other this is called connecting in series. This is shown below. To calculate the total overall resistance of a number of resistors connected in this way you add up the individual resistances. This is done using the following formula: Rtotal = R1 + R2 +R3 and so on. Example: To calculate the total resistance for these three resistors in series.

*Rtotal = R1 + R2 + R3* *= 100 + 82 + 1 Ohms* *= 183 Ohms *

Task 1:

Calculate the total resistance of the following resistor in series.

	Rtotal	= _______________
		= _______________

	Rtotal	= _______________
		= _______________

	Rtotal	= _______________
		= _______________

Resistors in Parallel

When resistors are connected across each other (side by side) this is called connecting in parallel. This is shown below.

Two Resistors in Parallel

To calculate the total overall resistance of a of two resistors connected in this way you can use the following formula:

Example: To calculate the total resistance for these two resistors in parallel.

Task 2:

Calculate the total resistance of the following resistor in parallel.

Three or more resistors in parallel

To calculate the total overall resistance of a number of three or more resistors connected in this way you can use the following formula: Example: To calculate the total resistance for these three resistors in parallel