A length of aluminum wire is connected to a precision 10.00-V power supply, and a current of 0.4076 A is precisely measured at 30.0∘C. The wire is placed in a new environment of unknown temperature where the measured current is 0.3502 A. The temperature coefficient of resistivity of aluminum is 0.00429. What is the unknown temperature?

Respuesta :

Answer:

[tex]68.3^{\circ}C[/tex]

Explanation:

The relationship between voltage, resistance and current in a metal wire is given by

[tex]V=RI[/tex]

where

V is the voltage

R is the resistance

I is the current

Moreover, the resistance of a metal wire as a function of the temperature is:

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

where

[tex]R_0[/tex] is the resistance at temperature [tex]T_0[/tex]

[tex]\alpha[/tex] is the temperature coefficient

In this problem, at 30.0∘C, we have

V = 10.00 V

I = 0.4076 A

So the resistance at this temperature is

[tex]R_0=\frac{V_0}{I_0}=\frac{10.00}{0.4076}=24.53 \Omega[/tex]

Then, at the unknown temperature T, the current is

I = 0.3502 A

So the resistance is

[tex]R(T)=\frac{V}{I}=\frac{10.00}{0.3502}=28.56\Omega[/tex]

Substituting and solving for (1), we find the unknown temperature:

[tex]T=T_0+\frac{\frac{R}{R_0}-1}{\alpha}=30.0+\frac{\frac{28.56}{24.53}-1}{0.00429}=68.3^{\circ}C[/tex]

The value of temperature in new environment is 68 degree Celsius.

The resistance is defined as ratio of voltage to the current.

     Resistance, [tex]R=\frac{V}{I}[/tex]

When voltage is 10.00-V power supply, and a current of 0.4076 A .

Resistance, [tex]R_{1}=\frac{10}{0.4076}=24.54ohm[/tex]

When voltage is 10.00-V power supply, and a current of 0.3502A

            [tex]R_{2}=\frac{10}{0.3502}=28.55[/tex] ohm

Here we use relationship,

             [tex]R_{2}=R_{1}(1+\alpha (T_{2}-T_{1}))[/tex]   and  [tex]T_{1}=30[/tex]

Where [tex]\alpha[/tex] is the temperature coefficient of resistivity.

Substituting all values in above equation

           [tex]28.55=24.54(1+0.00429(T_{2}-30))\\\\1+0.00429(T_{2}-30)=1.1634\\\\0.00429(T_{2}-30)=1.1634-1=0.1634\\\\(T_{2}-30)=38.09\\\\T_{2}=38.09+30=68.09[/tex]

Hence, The value of temperature in new environment is 68 degree Celsius.

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