Resistance and Temperature(isn't this right?)

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Homework Help Overview

The discussion revolves around a problem involving a platinum resistance thermometer used to determine the melting point of a substance based on its resistance at different temperatures. The context includes the application of a specific equation relating resistance and temperature, with a focus on the temperature coefficient of platinum.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of the resistance-temperature equation and express confusion over the results obtained. There is mention of using an online calculator that seems to confirm the original poster's answer, leading to questions about potential oversights or tricks in the problem.

Discussion Status

The discussion is ongoing, with participants exploring the validity of the calculations and considering factors such as significant figures that may affect the interpretation of the result. There is no explicit consensus on the correctness of the answer yet.

Contextual Notes

Participants are considering the implications of significant figures in their calculations, which may influence the final answer. There is also a suggestion that there could be additional considerations or tricks related to the problem that have not yet been addressed.

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Homework Statement



A platinum resistance thermometer has a resistance of 200 when placed in a ice 0◦C
bath and 280 when immersed in a crucible containing a melting substance. What is
the melting point of the substance? The temperature coefficient of the platinum is
0.00392(◦C)−1. Answer in units of ◦C.


Homework Equations



R = r [1 + a(T - t)]

The Attempt at a Solution



This looks like such a simple problem, just plug and chug, but I keep getting the wrong answer.

280 = 200 [1 + 0.00392(T - 0)]
1.4 = 1 + 0.00392T
0.4 = 0.00392T
T = 102.04
 
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Tekmachine said:

Homework Statement



A platinum resistance thermometer has a resistance of 200 when placed in a ice 0◦C
bath and 280 when immersed in a crucible containing a melting substance. What is
the melting point of the substance? The temperature coefficient of the platinum is
0.00392(◦C)−1. Answer in units of ◦C.

Homework Equations



R = r [1 + a(T - t)]

The Attempt at a Solution



This looks like such a simple problem, just plug and chug, but I keep getting the wrong answer.

280 = 200 [1 + 0.00392(T - 0)]
1.4 = 1 + 0.00392T
0.4 = 0.00392T
T = 102.04

The online calculator would seem to agree with your answer:
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/restmp.html#c3
 
Tekmachine said:
That's the calculator I used ^ ^, hmmmm is there something I'm forgetting to take into account? Maybe some sort of trick to the problem?

Perhaps the significant figures is in error? They would want only 102 C?
 

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