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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.
Direct Current Calculations
P = I V
P = V2 / R
P = I2 Rd
Alternating Current Calculations
To calculate RMS power, use RMS values for the voltage and current.
Vrms = 0.7 Vpeak
Irms = 0.7 Ipeak
Prms = Vrms2 / R
Prms = Irms2 R
Ohm's law states that current, voltage and resistance are related in the following three ways ...
and by substituting V you get ...
and by substituting I you get ...
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