When do I know which relation of heat to use with resistance like where to use directly proportional or inversely .
if a bulb is connected in series with two bulbs parallels to each other which formula should I useto find which is more bright? why can't I use heat directly proportional to power and the relation of power in series and parallel? How do I know which relation to use in a question because heat is directly proportional to resistance in one formula and inversely proportional to it in other?