If heat is directly proportional to resistance so why does the formula of Heat that is H=V²T/R
shows that these both terms are inversely proportional?
Answers
In equation H = I²Rt. If I is constant, only then you can say that H is directly proportional to R.
Illustration : Household electricity supply has a rating of 220V (in India), but current is not rated constant, i.e. the voltage (V) is constant but Current (I) is variable.
Therefore in Equation H = I²Rt, if we increase R, I will decrease (since I = V/R). Thus in this case based on this equation we cannot comment on the proportinality of H and R.
That is why we substitute the value of I = V/Rin equation H = I²Rt and obtain another equation H = V²t/R.
In this new equation V²t is a constant (V = 220 V).
Thus we can say H = k/R.
Or H is inversely proportional to R.
On the other hand if we have a constant current supply (certain batteries have a constant current rating), then equation H = I²Rt would make more sense in computing dependancy of H on R, and we will be able to say that H is directly proportional to R.
I hope you like my answer.