Potential difference is the work done per unit charge moving from one point in a circuit to another.

$$ W = QV $$

The work done moving an electron from one point in a circuit to another is found as

$$ W = eV $$

This gives rise to a new unit of electrical energy and used for energy of particles such as electrons or other particles with single charges.

Worth knowing

$$ 1 eV = 1.6 \times 10^{-19} J $$

Power is the rate of doing work. So in terms of electrical energy

$$ W = QV $$

So electrical power is

$$ P = \frac{W}{t} $$

$$ P = \frac{QV}{t} $$

$$ P = IV $$

So an LED running at 25 mA and 2.2 V has an electrical power of

$$ P = 25 \times 10^{-3} \times 2.2 $$

$$ P = 62.5 mW $$