Current divider calculator
Current divides in inverse proportion to resistance: I₁ = I × R2 ÷ (R1 + R2). One amp through a 100 Ω and a 300 Ω branch gives 0.75 A in the 100 Ω branch and 0.25 A in the 300 Ω one; the lower resistance takes the larger share.
How to use the current divider rule
The current divider looks like the voltage divider with the labels swapped, and that swap is exactly where mistakes happen. In a voltage divider the output uses the resistor it is measured across; in a current divider the branch current uses the opposite resistor in the numerator. The physical intuition is simple once seen: current takes the easier path, so the smaller resistance carries more. Its most common practical use is a shunt — putting a known low resistance in parallel with a meter movement so that a known fraction of the current bypasses it.
Questions
I₁ = I_total × R2 ÷ (R1 + R2). The opposite resistor appears on top.
Both branches see the same voltage, and current is voltage over resistance, so lower resistance means higher current.
For a branch among many, use I_branch = I_total × (R_parallel_of_all ÷ R_branch).
A low-value resistor in parallel with a meter so a known fraction of current bypasses it, extending the range.
No, and that is why they need individual resistors. Small differences in forward voltage cause large differences in current.