6.03 The current divider rule

The current divider rule can be used as a quick way of calculating branch currents when a current flows into a junction with two parallel branches.

current divider

proof of the current divider rule

  • I3 = VP/R3
  • VP = IT x RT
  • RT = (R2 x R3)/(R2 + R3)
  • Therefore VP = IT x (R2 x R3)/(R2 + R3)
  • Therefore I3 = IT x (R2 x R3)/(R2 + R3)/R3
  • Therefore I3 = IT x R2/(R2 + R3)

Note the format is almost identical to the voltage divider except that the resistor that is on the top of the resistor ratio in the equation is not the one we are calculating the current for.