**Sir, what is the difference between the formulas P=(I*I)R and P=(V*V)/R? On what context do we use the two?….A question by Rajit Roy.**

**This is a very good question and I thought of sharing the answer with you all.**

**The relation I^2R implies P proportional to R and is used when I is constant e.g. in a series combination of resistances I is same thro’ all the resistances.**

**V^2/R is used in a parallel combination of resistances. In this case V is constant and hence power is inversely related to R.**

P.S. :Use I^2 R for power loss in transmission.

### Like this:

Like Loading...

*Related*

Which one of the two should we use for calculating power loss in a transmission line?

I^2.R