- #1
DevonZA
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- 6
Homework Statement
Homework Equations
The Attempt at a Solution
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1. A copper rod, 100 mm long and 2.5mm diameter, has a resistance of 340micro ohms at 15degrees Celsius. If the rod is drawn out into a wire of uniform diameter 0.5mm, calculate its resistance at 60 degrees Celsius. Assume the temperature coefficient of resistance to be 0.0043/degree Celsius at 0 degrees Celsius.
2. R1/R2=1+alpha0xt1/1+alpha0xt2
3. (340 uohm)(L2/L1) / (R2/R1)^2
= (340 uohm)(2500/100)(2.5/0.5)^2 = 0.2125 ohms.
Then use the temperature equation:
R = (0.2125 ohm)(1 + 0.0043*45) = 0.25 ohms
^^ This is an answer that I found online but I don't know where the person got the 2500 value for L2 from?
The answer given in the textbook is R=0.251ohms
Thanks,
Devon.