1. The problem statement, all variables and given/known data How does emf relate to current, electrical potential, and resistance? Specifically, in the context of the equations I have posted below. 2. Relevant equations V = IR where V is electric potential, I is current, and R is resistance. V = emf - IR How can V = emf - IR if V = IR ? Here is another similar example: R = V/I R = (emf - V) / I 3. The attempt at a solution emf seems to be some kind of change to the original electric potential of a circuit. emf - IR seems to calculate ΔV. Am I right about this? As far as I can tell, Ohm's law uses V, not ΔV. When is ΔV useful and when is V useful? Or do I have this all wrong? Thanks.