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Formula for electric power?….A good question……

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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.

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2 Comments

  1. Rajit Roy says:

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

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