1. The problem statement, all variables and given/known data We have an ammeter with 20Ω resistance and a range of 10mA or 0.01A. The different ranges are 3000mA, 300mA, 30mA. Calculate the shunt resistors a, b and c. 2. Relevant equations 3. The attempt at a solution Ia = 0.01A ; Ra = 20Ω ; I = 0.03A Ua = Ia ⋅ Ra = 0.01A ⋅ 20Ω = 0.2V Is = I - Ia = 0.03A - 0.01A = 0.02A The multiplication factor: m = I / Ia = 0.03 / 0.01 = 3 I found the equivalent resistance for all shunts: Rn = Ra / m - 1 Rn = 20 / 3 - 1 = 10Ω In parallel the voltage is the same in all resistors, but a, b and c are in series and have their own voltages out of our Ua = 0.2V. How can I find the voltage for a, b and c? Otherwise I can't calculate each resistor. The answers on my answer sheet are: a = 0.1Ω b = 0.9Ω c = 9Ω So indeed the equivalent resistor is 10Ω. I hope someone can help me with this.