Electric power is the rate of energy consumption in an electrical circuit.

The electric power is measured in units of watts.

- Electric power definition
- Electric power calculation
- Power of AC circuits
- Power factor
- Power calculator

The electrical power P is equal to the energy consumption E divided by the consumption time t:

P is the electrical power in watts (W).

E is the energy consumption in joules (J).

t is the time in seconds (s) .

Find the electrical power of a circuit that consumes 120 joules for 20 seconds.

Solution:

*E* = 120J

*t* = 20s

*P* = *E* / *t* = 120J / 20s = 6W

*P* = *V *⋅* I *

or

*P = I ^{ }*

or

*P = V ^{ }*

P is the electrical power in watts (W).

V is the voltage in volts (V).

I is the current in amperes (A) . .

R is resistance in ohms (Ω).

Formulas apply to single-phase AC power.

For 3-phase AC:

If you use the phase-to-phase voltage (VL-L) in the formula, multiply the single-phase voltage - Phase power divided by the square root of 3 (√3=1.73).

When the line is at zero voltage (VL- 0 ) is used in the formula, multiply the single-phase power by 3.

Real power or true power is the power used to do work on of the load .

*P* = *V _{rms}*

*P *is the real power in watts
[W]

V_{rms} is the rms voltage = V_{peak}/√2
in Volts [V]

I_{rms} is the rms current = I_{peak}/√2
in Amperes [A]

*φ * is the* *impedance phase angle = phase difference
between voltage and current.

Reactive power is the power that is wasted and not used to do work on the load.

*Q* = *V _{rms}*

*Q *is the reactive power in
volt-ampere-reactive [VAR]

V_{rms} is the rms voltage = V_{peak}/√2
in Volts [V]

I_{rms} is the rms current = I_{peak}/√2
in Amperes [A]

*φ * is the* *impedance phase angle = phase difference
between voltage and current.

The apparent power is the power that is supplied to the circuit.

*S* = *V _{rms}*

*S *is the apparent power in
Volt-amper [VA]

V_{rms} is the rms voltage = V_{peak}/√2
in Volts [V]

I_{rms} is the rms current = I_{peak}/√2
in Amperes [A]

The real power P and reactive power Q give together the apparent power S:

*P*^{2} + *Q*^{2} = *S*^{2}

*P *is the real power in watts
[W]

*Q *is the reactive power in
volt-ampere-reactive [VAR]

*S *is the apparent power in
Volt-amper [VA]

- Power calculator
- Power factor calculator
- Power factor
- Watt (W)
- dB-milliwatt (dBm)
- dB-watt (dBW)
- Kilowatt (kW)
- Kilovolt-amp (kVA)
- Efficiency
- Electrical voltage
- Electrical current
- Electric charge
- Power conversion
- Ohm's law

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