What is v in p=IV if I want to use p=IV to calculate power loss
Yes, both of those V represent the voltage drop.

The formula P=(I^2)R is for the case of constant current and (V^2)/R is used for the case of constant voltage.

Considering a constant voltage source, we can see that when the resistance increases, the current decreases. Ultimately it comes down to P=IV. So at constant voltage, power is inversely proportional to resistance.

In case of constant current source, when there is increase in resistance, more voltage is dropped(Ohm's law). So again using P=IV, power is directly proportional to the voltage and voltage is directly proportional to the resistance.

It all depends on your choice.You can use all three formulas if you know all the parameters. Check it yourself.







simulate this circuit &ndash; Schematic created using CircuitLab

Find the current and voltage drop across each resistor. Now apply all three formulas. Compare the results.