Hey, I got this question in a homework from a teacher of mine: "A car battery with a 15.0 V emf and an internal resistance of 0.0430 is being charged with a current of 62.5 A. What is the potential difference across its terminals?" I've tried nearly every formula I know on it. EMF = IR + Ir gives me: 15.0 = (62.5 x R) + (62.5 x 0.0430) 15.0 = (62.5 x R) + 2.6875 62.5 x R = 12.3125 R = 0.197 If I then use that value in V = IR I get: V = 62.5 x 0.197 = 12.3125 I tried that answer but it's incorrect...please, this is driving me nuts! Can anyone help me out? Does this seem like an incredibly hard question for a 16 year old?!?!?!