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Resistance in parallel

Resistance in parallel formula

Section titled “Resistance in parallel formula”

When resistors are connected in parallel, the total or equivalent resistance () can be calculated using the formula:

We can re-arrange this to find :

… where , , , … are the resistances of the individual resistors connected in parallel.

Calculate the resistance of two resistors in parallel

Section titled “Calculate the resistance of two resistors in parallel”
           +-------+
        +--| 12ohm |--+
        |  +-------+  |
        |             |
--------+             +--------
        |             |
        |  +-------+  |
        +--| 18ohm |--+
           +-------+
  • Total resistance, :

Increasing the number of resistors in parallel

Section titled “Increasing the number of resistors in parallel”

If we add more resistors in parallel, the equivalent resistance decreases. This is because adding more paths for the current to flow reduces the overall resistance of the circuit (because there are more pathways for the electrons to ‘choose’).