Electrical power and Joule heating
Voltage times signed current measures element power.
Key knowledge
With passive sign convention, current entering an element’s higher-potential terminal gives absorbed instantaneous power p=vi and energy ∫pdt. For a positive constant resistance, p=i²R=v²/R≥0: electrical energy becomes internal energy and other dissipation channels. AC average power is the average of vi, rather than generally the product of rms voltage and rms current.
Values and equations
p=vi; E_absorbed=∫pdt; p_resistor=i²R=v²/R
- p,p_resistor
- Instantaneous absorbed power and resistor dissipation W
- v
- Voltage with the passive terminal polarity V
- i
- Current entering the positive voltage terminal A
- R
- Positive resistance Ω
- E_absorbed
- Net energy absorbed over the interval J
- t
- Time s
Conditions and scope
- Lumped two-terminal element in the stated quasistatic circuit regime; sign current and voltage consistently.
- The resistor formulas require its ohmic relation at the actual conditions. Reactive elements can temporarily return stored energy; changing fields outside a lumped model require electromagnetic energy-flux accounting.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read §9.5 charge-energy/power9.17 and Joule-power9.18. Passive sign and time integration are disclosed refinements; the AC qualification bounds the instantaneous expression rather than claiming an independently sourced AC power-factor formula.
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Entry details
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- foundation-physics-electrical-power
- Revision
- foundations-refresh.1
- Structured reference record
- Foundational reference additions