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## Homework Statement

ti[/B]A resistance thermometer, which measures temperature by measuring the change in resistance of a conductor, is made of platinum and has a resistance of 50.0 Ohms? at 20.0°C.

**(a)**When the device is immersed in a vessel containing melting indium, its resistance increases to 76.8 Ohms?. From this information, find the melting point of indium.

**(b)**The indium is heated further until it reaches a temperature of 235°C. What is the ratio of the new current in the platinum to the current

*I*mp at the melting point?

## Homework Equations

## R = R_0 [1+\alpha(T-T_0)] ##

##\alpha_{plat} = 3.92 \cdot 10^{-3}##

## The Attempt at a Solution

For part (a), the answer is 157 degrees Celsius. (Says in the book as well)

Now, I'm getting 2 different answers for part (b) when using ## T_0 = 20## and ##T_0 = 157##.

When ##T_0 = 20##, the final resistance is ##50[1+\alpha \cdot 215] = 92.14##

When ##T_0 = 157##, the final resistance is ##76.8[1+\alpha \cdot 78] = 100.2##

Why the large discrepancy with calculating the same thing? (The 2nd one is correct, per the book)

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