Internal Resistance of DC Power Supply · Physics Brawl 2025 #5
Physics · electromagnetism
Problem
David found an old DC power supply. He was wondering about how to use it, so he tried to connect it into a circuit with 2 resistors with the resistance of R=10 Ω. In the first case he connected them in series, then parallel. In both cases he measured the current in the circuit. In the first case he measured the current as I1=1.2 A and in the second one as I2=4.0 A. David knew that the power supply is not ideal. Calculate the internal resistance of the power supply.