Here is the question I need to solve: A battery has an emf E and an internal resistance r. When the battery is connected to a 25 ohm resistor, the current through the battery is 0.75 A. When the battery is connected to a 53 ohm resistor, the current is 0.45 A. Find the emf of battery and its internal resistance. Okay, so I have a feeling I will be using the equation V = IR, but I don't knnow how to incorporate an internal resistance into the equation or approach. Can someone please help me outline the steps to solve this? Thanks!