What is the formula used to calculate electrical power in a dc circuit?

Electric power is a measure of energy per unit of time.

For example: 1 volt=1 joule (energy)/ 1 coulomb (electric charge)

1 ampere=1 coulomb/1 second

1 watt=1 joule/1 second

In a direct current circuit, P (watts)=V (volts) x I (amps)

For direct current:

P=VxI

P=I^2R

P=V^2/R

Where R is resistance (ohms).

For alternating current:

S=P+jQ

S=VI* (I* means complex conjugate of I)

S=sqrt(P^2+Q^2)

V=IxZ

Z=R+jX

So P is the real part of S and Q is the imaginary part of S.

S is in unit of volt-amperes, P is in watts and Q is in vars (volt-ampere reactive).

X is reactance and is calculated by either jwL or 1/jwC or both depending on what components are in the circuit.

w is 2xpixfrequency of the AC circuit. L is inductance and C is capacitance.

CommentThere is no such thing as 'electrical power'. Power is simply a rate -it is neither electrical, mechanical, or anything else!