For a two-terminal element or a two-terminal circuit with terminals A and B, $\textit{Instantaneous Power}$ is the product of the voltage $u_{AB}$ between the terminals and the electric current i in the element or circuit: $$p = u_{AB} \cdot i$$ Where $u_{AB}$ is the line integral of the electric field strength from A to B, and where the electric current in the element or circuit is taken positive if its direction is from A to B and negative in the opposite case. $$$$ For an n-terminal circuit, it is the sum of the instantaneous powers relative to the n - 1 pairs of terminals when one of the terminals is chosen as a common terminal for the pairs. $$$$ For a polyphase element, it is the sum of the instantaneous powers in all phase elements of a polyphase element. $$$$ For a polyphase line consisting of m line conductors and one neutral conductor, it is the sum of the m instantaneous powers expressed for each line conductor by the product of the polyphase line-to-neutral voltage and the corresponding line current.
$p = ui$, where $u$ is instantaneous voltage and $i$ is instantaneous electric current.
Applicable units are those of quantitykind:ElectricPower
Instantaneous Power