Current Divider

Formula

Description

The current divider rule describes how current splits between parallel branches inversely proportional to their resistance. A branch with lower resistance carries more current, while a branch with higher resistance carries less. This is the dual of the voltage divider and follows directly from the fact that parallel branches share the same voltage. Notice the counterintuitive cross-relationship: the current through R1 depends on R2, not R1, because the shared voltage is set by the parallel combination.

Variables

• Itotal — Total current entering the parallel network (A)
• R1 — Resistance of branch 1 (Ω)
• R2 — Resistance of branch 2 (Ω)
• I1 — Current through R1 (A)

Practical Notes

For more than two parallel branches, use I_k = Itotal × (Rtotal / Rk) where Rtotal is the parallel combination of all branches. Current dividers are fundamental to understanding transistor biasing and current mirror circuits.