P=vi

[MedPR]

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You can derive a few different power equations from V=IR.

1. P=VI
2. P=I^2R
3. P=V^2/R

Equation 2 says that if you increase resistance, you increase power.

Equation 3 says that if you increase resistance, you decrease power.

???

 

[milski]

You can derive a few different power equations from V=IR.

1. P=VI
2. P=I^2R
3. P=V^2/R

Equation 2 says that if you increase resistance and hold current constant, you increase power.

Equation 3 says that if you increase resistance and hold the potential constant, you decrease power.

???

Because of V=IR you cannot change just the resistance. It makes sense to keep either I or V constant. Of course you could change all three of them but that can lead to anything.

 

[TXKnight]

You can derive a few different power equations from V=IR.

1. P=VI
2. P=I^2R
3. P=V^2/R

Equation 2 says that if you increase resistance, you increase power.

Equation 3 says that if you increase resistance, you decrease power.

???

Eq. 2 is for Power dissipated?....milski might have it right

 

[TopPops]

You can derive a few different power equations from V=IR.

1. P=VI
2. P=I^2R
3. P=V^2/R

Equation 2 says that if you increase resistance, you increase power.

Equation 3 says that if you increase resistance, you decrease power.

???

Equation 2, if you increase resistance, power dissipated increases only if the current is kept constant which means resistors must be in series.

Equation 3, if resistance increases, power dissipated through that resistor decreases if voltage is kept constant which means resistors are in parallel

 

[SaintJude]

Wow milski. You've actually done the impossible. You answered my exact question before I even asked it.

I knew that Eq.2 and Eq.3 were only applicable to limited scenarios, (but didn't know what they were exactly) Given those limitations, that's why those conclusions are valid.

Only P=IV is universally applicable then?

 

[milski]

Wow milski. You've actually done the impossible. You answered my exact question before I even asked it.

I knew that Eq.2 and Eq.3 were only applicable to limited scenarios, (but didn't know what they were exactly) Given those limitations, that's why those conclusions are valid.

Only P=IV is universally applicable then?

All of them are applicable - they are equivalent. But if you are changing both I and R, you cannot tell anything about the I^2/R without knowing how much you're changing each. Which you could get from P=IV or V=IR but you cannot tell just by looking at I^2/R.