How to Solve a Series and Parallel Circuit With One Power Supply

Series Circuit

• 1

  Look for the voltage measurement on the diagram. For example, assume you have a 6-volt DC circuit.

• 2

  Look for all resistors on the circuit. Resistors are indicated by zig-zag lines and labeled with the ohm rating. For example, assume you have a 2-ohm, a 4-ohm and a 6-ohm resistor on this circuit.

• 3

  Add the values of the resistors. These three resistors provide a total resistance of 12 ohms.

• 4

  Divide the voltage by the resistance to determine the current: 6 divided by 12 is 0.5; this series circuit has a current of 0.5 amperes per Ohm's Law.

Parallel Circuit

• 5

  Locate the power supply. In this example, assume a 20-volt DC circuit.

• 6

  Locate the resistors on the diagram and take the reciprocal of each value. For example, a 2-ohm, a 5-ohm and a 6-ohm resistor have reciprocals of 0.5, 0.2, and 0.167.

• 7

  Add these values to determine the total resistance. This parallel circuit has a total resistance of 0.867 ohms.

• 8

  Use Ohm's Law to determine the current: 20 volts divided by 0.867 ohms equals 23.06 amperes.