Electric Power
Electric power is the rate at which electrical energy is consumed or supplied. P = VI = I²R = V²/R. Unit is the watt (W).
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Definition of electric power
Electric power P is the rate at which electrical energy is transferred or consumed. P = E/t = VI. The SI unit is the watt (W): 1 W = 1 J/s = 1 V·A. So a device with a potential difference V across it and current I through it dissipates power P = VI.
Forms of the power formula
Using Ohm's law V = IR, we get P = VI = I²R = V²/R. So for a resistor, power can be calculated from any two of V, I, and R. Power is dissipated as heat (Joule heating) in resistors.
Ratings of appliances
Appliances are rated by power (e.g. 100 W bulb, 1 kW heater). Higher power means more energy consumed per second. Fuses and circuit breakers are chosen to limit current so that power loss and heating stay safe.
A 100 W bulb and a 25 W bulb both run at the same voltage. Which has the higher resistance, and why?