Temperature variation of resistance

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SUMMARY

The discussion centers on calculating the resistance of a metal wire at -20°C using the resistance values at 20°C and 90°C. The resistance at 20°C is given as 8.10 ohms, and at 90°C, it is 11.45 ohms. The temperature coefficient of resistance (alpha) is calculated as 4.18e-3. Using the formula R=R(o)[1+alpha(T-To)], the resistance at -20°C is determined to be approximately 6.746 ohms, which is within 10% of the correct value.

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dasblack
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Homework Statement


A metal wire has a resistance of 8.10 at a temperature of 20°C. If the same wire has a resistance of 11.45 at 90°C, what is the resistance of the wire when its temperature is -20°C?


Homework Equations


R=R(o)[1+alpha(T-To)]
alpha=R-Ro/Ro(T-To)


The Attempt at a Solution


alpha=11.45-8.1 / 11.45(70) = 4.18e-3
R=11.45[1+(4.18e-3)(-40)] = 9.54 ohms
But 9.54 isn't the answer...
 
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dasblack said:

The Attempt at a Solution


alpha=11.45-8.1 / 11.45(70) = 4.18e-3
R=11.45[1+(4.18e-3)(-40)] = 9.54 ohms
But 9.54 isn't the answer...


Isn't the resistance at 20° = 8.1?
 
LowlyPion said:
Isn't the resistance at 20° = 8.1?

Hmm.. I did that and got 6.746. It says I am within 10% of the correct value
 

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