The thermal energy developed in a current-carrying resistor is given by U = i2Rt and also by U = Vit. Should we say that U is proportional to i2 or to i?
In the expression
both V and i are time dependent quantities and hence we cannot say that U is proportional to i. However, in the expression
only i is the time dependent quantity and hence we can say that U is proportional to i2.
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