Calculating Power Dissipated

[charistivity]

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Does anyone know when to use the different power formulas P= IV, P=I^2R and P=V^2/R

I have seen and read various interpretations as to which one is more appropriate in a given situation but I don't just get it. Some explanations also seem to be conflicting. My most recent example of this was from a review material: to minimize P dissipated by the wires, they (power companies) minimize I by maximizing V. This is why power lines transfer electricity at high voltage.

Wouldn't increasing V result in increased power dissipation using P = IV or P = V^2/R?

I would really appreciate it if someone could help me put this thing to rest.

 

[erythrocyte666]

You'd obviously use the eqn based on what's given.
As for choosing b/w V2/R and I2R, it comes down to whether voltage or current is constant. If you had 2 different resistors in parallel connected to a battery, V2/R would be more apt (but you could use I2R if you knew currents through both). Similarly, I2R is more apt for 2 different resistors in series.