Sim's Electrical Companion
Power Law
Power is the product of voltage and current. The unit for power has been attributed to James Watt, a Scottish engineer, he dedicated much of his life to improving the performance & design of steam engines.
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The SI unit for power is Watt (W) and in purely resistive DC circuits is the product of Voltage x Current. So power is the product of the electromotive force (emf) and quantity of charge that is being moved by that force.
With this extra element to consider it is worth applying power law to the series and parallel circuits used to explain Kirchhoff's and Ohm's law.
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So if we revisit the first circuit in a purely resistive series circuit we can now calculate the power consumed by the entire circuit and the individual elements that make up that circuit.
The first series circuit was a combination of three loads 10Ω, 15Ω and 30Ω. The applied voltage is 165V and the total current flowing through the circuit is:
V / R = I = 165V / 55 Ω = 3 Amps
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As we have the two other parts of the equation we can calculate power for the circuit as a complete entity:
The first series circuit was a combination of three loads 10Ω, 15Ω and 30Ω. The applied voltage is 165V and the total current flowing through the circuit is:
V / R = I = 165V / 55 Ω = 3 Amps
​
As we have the two other parts of the equation we can calculate power for the circuit as a complete entity:
