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To what value would you have to raise the temperature of a copper wire (originally at 20 ∘C) to increase its resistance by 17 % ?

Answer :

Answer:

The temperature is   [tex]   T_2=  63.59 ^oC[/tex]

Explanation:

Generally the equation that represents the variation of resistance with respect to temperature is mathematically  represented as      

   [tex]R = R_i (1 +  \alpha *  \Delta  T  )[/tex]

=>  [tex]R = R_i (1 +  \alpha *  [T_2 -  T_1] )[/tex]

Here  [tex]T_1[/tex] is the original  temperature with value  [tex]T_1 = 20^oC[/tex]  

     [tex]R_i[/tex] is the initial resistance of the copper

         R is the resistance at  temperature [tex]\Delta  T[/tex]

[tex]\alpha[/tex] is the temperature coefficient of resistivity with a value  

     [tex]\alpha =3.9 *10^{-3} \  ^oC^{-1}[/tex]

From the question we are told that  

      [tex]R =  17\% \  of  R_i + R_i [/tex]

So

      [tex]R =  0.17R_i + R_i [/tex]

       [tex]R =  1.17R_i [/tex]

Hence

     [tex]1.17 R_i = R_i (1 + 3.9 *10^{-3}  *  [T_2 -  20] )[/tex]

    [tex]1.17  =  (1 + 3.9 *10^{-3}  *  [T_2 -  20] )[/tex]

=>    [tex] 0.17 = 3.9 *10^{-3}  *  [T_2 -  20] )[/tex]

=>   [tex]   [T_2 -  20]  = 43.5897 [/tex]

=>   [tex]   T_2=  63.59 ^oC[/tex]

     

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