NCCER Introduction To Electrical Circuits (26103-23) Practice Test

Understanding voltage terminology: EMF, or electromotive force, is another term used for voltage. It describes the energy per unit charge that a source can supply to move charges through a circuit, which is what drives current. In an ideal source with no internal resistance, the emf equals the voltage you measure at the source’s terminals when no load is connected. In real sources, internal resistance causes a small drop, so the terminal voltage under load is emf minus the I·R drop. Voltage is the general term for the potential difference between two points, which can be across a component or a source, while emf specifically refers to the driving potential generated by a source. Current is the rate of charge flow, not a measure of potential difference, and power is the rate of doing work, equal to voltage times current.