#
Formula: **Electric power**

$$P ~=~ U \, I$$
$$P ~=~ U \, I$$
$$I ~=~ \frac{P}{U}$$
$$U ~=~ \frac{P}{I}$$

## Electric power

`$$ P $$`Unit

`$$ \mathrm{W} = \frac{\mathrm J}{\mathrm s} $$`

Electric power is the energy supplied to or dissipated from an electrical circuit, resistive element, etc., per unit time.

\(P\) is the energy per time dissipated from the circuit by heating the resistor. Without a voltage source to supply the energy, the circuit would quickly lose its energy in the form of heat and the current would drop to zero. In an ideal, resistanceless circuit (see superconductivity), on the other hand, the energy is not lost and the current is maintained for many years; ideally, for an infinite time.

Example: To operate a \( P = 60 \, \mathrm{W} \) light bulb, with \( U = 230 \, \mathrm{V} \) voltage, a current of \( I = 0.261 \, \mathrm{A} \) is needed.

## Electric current

`$$ \class{red}{\boldsymbol I} $$`Unit

`$$ \mathrm{A} = \frac{ \mathrm C }{ \mathrm s } $$`

Electric current is the amount of charge that flows per unit time through a resistive element.

## Voltage

`$$ U $$`Unit

`$$ \mathrm{V} = \frac{ \mathrm J }{ \mathrm C } = \frac{ \mathrm{kg} \, \mathrm{m}^2 }{ \mathrm{A} \, \mathrm{s}^3 } $$`

Voltage represents the energy (per charge) that a charge would gain or lose if it were to pass through a circuit element (e.g. a resistor) to which this voltage is applied.