Uncertainty formula in resistor

AI Thread Summary
The discussion revolves around calculating the uncertainty in power loss (P) in a resistor using the formula P = V^2/R. Given uncertainties of 3% in voltage (V) and 2% in resistance (R), participants clarify that the fractional error for V should be doubled due to the square relationship, resulting in 6%. They emphasize that uncertainties should be added, not subtracted, leading to a total uncertainty of 8%. The correct answer to the original question is determined to be option C, 8%.
jinx007
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I am having a lot pf problem to attempt this question, please help me, i am stuck..!

The power loss P in a resistor is calculated using the formula p=v^2/R

The uncertainty in the potential difference V is 3% and the uncertainty in the resistance R is 2%. What is the Uncertainty in P?

A/ 4%

B/ 7%

C/ 8%

D/ 11%

Hmmm My attempt:

Fractional error = in V, 0.09 and in R 0.2 i subtracted and i got 0.11 that is 11% ANSWER D

And i can be at 98% sure that the answer is not correct as uncertainty cannot be substrate d ..? please help me to attempt the question !
 
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the fractional error in V is 6% (3% x 2), not 9%. if it's a square, the fractional error doubles; if it is a cube, the fractional error triples; and so on...

the fractional error in R is 2%.

ADD them up. If I remember correctly you never subtract any fractional error. it just add them all.

The answer should be C, 8%.
 

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