The thermal energy developed in a current carrying resistor is given by U= i(sq)RT and also U= vit. should we say that U is prpoportional to i(sq) or i ?

sq= square

We can say that,U is proportional to i² because resitance(R) of a particular material and time taken can be kept constant.

however,"v" and "i" are proportional to each other and so when "v" changes "i" changes, so it cannot be considered as a constant term

therefore, U is not proportional to i