Special case for just two resistors in parallel,

  • When two resistors are in parallel, the equivalent resistance is the product of the two resistors divided by their sum.

  • When the two resistors have the same value, the equivalent parallel resistance is exactly half of the original resistance.

Created by Willy McAllister.

Parallel resistors simulation model

  • Compute the equivalent parallel resistor using the formula from this video,

$\qquad\text R_\text{equiv} = \dfrac{\text R1\,\text R2}{\text R1 + \text R2}$

  • Find the current in the equivalent resistor,

$\qquad i = \text V1/\text R_\text{equiv}$

  • Click on DC to see what the simulator thinks. Compare your answers.

  • Make the two resistors the same value.
  • Compute the equivalent parallel resistor in your head. Change $\text R_\text{equiv}$ to that value.
  • Compute the current in the equivalent resistor in your head.
  • Click on DC to simulate. Compare your answers.