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प्रश्न
Define electric power. An electrical device of resistance R is connected across a source of voltage V and draws a current I. Derive an expression for power in terms of current and resistance.
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उत्तर
Electric power is defined as the rate of consumption of energy or simply the rate of doing work.
i.e., power, P =`(" work done"("W"))/("Time"("t"))` ..............(i)
The work done by current (I) when it flows in a potential (V) for time (t) can be given by
W = VIt …………………. (ii)
⇒ Power, P `= "VIt"/"t"="VI"`
∴Electric power, P = VI
From Ohm's law, V=VI
Thus, electric power is given by, P = (IR)I = I2R
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