Question

We use two expressions (i) H=I^2Rt and (ii) H=V^2/Rt for calculating the energy consumed by a device . out of these two expressions the first expression indicates that the energy consumed is directly proportional to R whereas the second expression indicates that the energy consumed is inveresely proportional to R .How can we explain the seemingly different dependence of H on R in these expressions ?

Answer 1

Dear student,
According to joules law of heating,in the expression $H=I^{2}Rt$ ,the heat produced is directly proportional to resistance of wire when the current flowing through the resistor is constant.

In the expression , H=v² /Rt the heat produced is inversely proportional to resistance of wire when voltage across the resistor is constant.

Regards.