Question

According to joule's law of heating, H=VIT,on applying Ohm's law, we get H=I^2RT.....so heat is directly proportional to resistance.......however if we substitute I=V/R(from Ohm's law), we get H=V^2T/R,that is heat is inversely proportional to resistance.......how can the same heat be directly and inversely proportional to same resistance by applying the same formula in two different cases?

Answer 1

Explanation:

When considering a two circuits connected in series to a battery, Current will be same but voltage is different.

So for a given resistance, Heat will be,

$h = {i}^{2} rt$

When we consider two circuits connected in parallel to a battery, Voltage will be same but current is different.

So for a given resistance, Heat will be

$h = \frac{ {v}^{2} }{r} t$