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A level Physics Uncertainty MCQ help!

Measurements are taken to determine the resistivity of a uniform metal wire. The table shows the
quantities measured and their percentage uncertainties:
Quantity - Percentage uncertainty
potential difference across wire - 0.3%
current in wire - 5.0%
diameter of wire - 4.0%
length of wire - 0.2%

What is the percentage uncertainty in the calculated value for the resistivity of the metal of the
wire?


The answer is 13.5%

I keep getting 9.5% by basically summing all the values ( as in teh equation they are all either multiplied or divided by)

Any help appreciated!
How does the resistivity of the wire depend on diameter?
Reply 2
Original post by lordaxil
How does the resistivity of the wire depend on diameter?

OH i see! Is it because the radius is squared so you add the uncertainty twice? Thank you :smile:

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