Question

how to know which equation to use to find power?
there's
P=IV
P=V^2/R
P=I^2R

Answer 1

When resistor is given, use any of those two that has R in its formula. When its not given, use the p=iv. Thanks!

Answer 2

so is it that we can use any formulas so long as those info are given? we don't have to care if things are ideal or whether there's heat loss something like this?

Answer 3

actually there are constraints but those are applied only when there are cmplex circuits .
one element circuits won't cause a prob