Electrical Power Loss Equations Confusion

[Kevin Shen]

Why is the equation Power Loss = I^2*R rather than Power Loss = V*I?
What I mean is why use I/R to represent V?
Also if Power Loss is equivalent to V*R, doesn't step up transformers which creating higher voltage also cause Power Loss to increase which contradicts to textbooks stating that power loss decreases if voltage rises given that power supply is same?

 

[scottdave]

You could use V*I or V^2/R to represent power (not V*R). But you need to understand how to use it. Look at a resistor. If the resistor has 50 ohms, and there is 10 volts across it, how do you find the power dissipated in the resistor? You can find the current in the resistor, then multiply current x voltage (across the resistor). If you look at Ohm's Law [V = I*R, not I/R], then you can substitute one of these values for it's equivalent combination of the other 2.

 

[russ_watters]

Why is the equation Power Loss = I^2*R rather than Power Loss = V*R?What I mean is why use I/R to represent V?

Power isn't V*R it is either V²/R or V*I. And V isn't I/R, it is I*R.

But in either case, as said above you can use different equations for different problems depending on what you need.

 

[Kevin Shen]

Power isn't V*R it is either V²/R or V*I. And V isn't I/R, it is I*R.

But in either case, as said above you can use different equations for different problems depending on what you need.

Yeah I realized I made the error and I get it now :)