Power 

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_{ a}
One Watt is the same as One Joule per Second.
Circuits consume energy from the power supply and produce energy at the output in the form of movement, light, sound, heat and so on. Circuits also produce waste heat energy.
_{ b}In the diagram, the power in Watts is dissipated as heat by the resistor. To prevent overheating, the resistor power rating must be sufficient. 
_{ c}Direct Current CalculationsP = I V P = V^{2} / R P = I^{2} R _{ d}Alternating Current CalculationsTo calculate RMS power, use RMS values for the voltage and current. V_{rms} = 0.7 V_{peak} I_{rms} = 0.7 I_{peak}
P_{rms} = V_{rms}^{2} / R P_{rms} = I_{rms}^{2} R 
Ohm's law states that current, voltage and resistance are related in the following three ways ...
Starting with
and by substituting V you get ...
Starting with
and by substituting I you get ...
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