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A platinum resistance thermometer has a resistance of 11.50 ohms at 0 oC and 17.35 ohms at 100 oC. Assuming that the resistance changes uniformly with temperature, what is the temperature when the resistance is 13.50 ohms?

Respuesta :

Answer:

[tex]34.2^{\circ}C[/tex]

Explanation:

The resistance increases linearly with the temperature - so we can write:

[tex]\Delta R = k \Delta T[/tex]

where

[tex]\Delta R[/tex] is the change in resistance

k is the coefficient of proportionality

[tex]\Delta T[/tex] is the variation of temperature

In the first part of the problem, we have

[tex]\Delta R = 17.35 - 11.50 =5.85\Omega[/tex]

[tex]\Delta T = 100 -0 = 100^{\circ}C[/tex]

So the coefficient of proportionality is

[tex]k=\frac{\Delta R}{\Delta T}=\frac{5.85}{100}=0.0585 \Omega ^{\circ}C^{-1}[/tex]

When the resistance is [tex]R=13.50\Omega[/tex], the change in resistance with respect to the resistance at zero degrees is

[tex]\Delta R' = 13.50-11.50 = 2.00 \Omega[/tex]

So we can find the change in temperature as:

[tex]\Delta T' = \frac{\Delta R}{k}=\frac{2.00}{0.0585}=34.2^{\circ}[/tex]

So the new temperature is

[tex]T_f = T_0 + \Delta T' = 0+34.2 = 34.2^{\circ}C[/tex]