The MCAT has been known to ask questions involving the distinction between the total EMF produced by a galvanic cell and the voltage supplied to the external circuit elements. Remember that the power cell or battery in a DC circuit supplies the electromotive force (emf), or voltage, to the entire circuit, not just the external circuit elements, but also including the power source's internal resistance. This means that the external voltage of the battery will be less than the emf because it also takes work to move charges over the internal resistance. Because V = e - IR, when the current is zero, the external voltage equals the EMF.