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Sign convention for power in an electrical circuit

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These problems on circuit analysis have been solved step by step, explaining the sign convention of electric power.

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Sign convention for power in an electrical circuit

In any electrical circuit, power absorbed by some of the circuit devices must be equal to the power delivered by some other circuit devices. This is the law of conservation of energy as applicable to an electrical circuit.. This can also be stated as : Algebraic sum of power delivered or absorbed (i.e. energy delivered or absorbed per second) by different circuit devices in an electrical circuit must be zero. From this definition, need for a sign convention is clear, because to find the algebraic sum we must assign a +ve or -ve sign to the power associated with a circuit device. Hence the following sign convention :

When current enters the positive terminal of a circuit element, power is given to the circuit element. This power may either be stored in the element as in case of a battery, capacitor and inductor or it could be dissipated as heat as in case of a resistance. When power is given to the circuit element it is taken as positive.

When current leaves the positive terminal (and enters the negative terminal) of a circuit element, power is given by the circuit element. When power is given by the ...

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