Fundamentals of Electrical Networks Current Voltage Power and Energy Active Elements Independent Sources Passive Elements Inductor Behaviour of Inductor for Ac and Dc Sources Capacitor Source Transformation Rules Impedance & Admittance Star - Delta Transformations

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Power is defined as the rate of energy transfer or rate of doing work. Power is expressed by the product of voltage and current. From the equation (1) and {2), we represent power measured in watts as

$P=v\;\times\;i\;=\;\frac{dw}{dq}\times\frac{dq}{dt}=\frac{dw}{dt}$ (3)

$w=\int_0^tp\operatorname dt$ (4)

Example: Find the power in watts if the applied constant voltage is 100 V and the current flowing in the circuit is 0.5 A.

$p= vi = 100\times0.5 = 50W$

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