Which statement describes an electrical source of 5V?

Emf is the work done (energy needed) to carry a unit charge (1C) through the whole complete circuit.

By definition, it is with respect to a unit charge (1C).

In general, it can also mean what is the emf when a certain amount of energy is carry certain amount of charge round the complete circuit.

Using V = E/Q, as long as the V is 5V, it is correct.

Note that 1C is NOT 1 electrons. The amount of charge on an electron is about 1.6 x 10^-19 C. So there are many electrons in 1 C.

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