Respuesta :
Given that the length of the wire is l = 40 ft = 12.192 m
The radius of the wire is
[tex]\begin{gathered} r\text{ = 2.59 m}m \\ =2.59\times10^{-3}\text{ m} \end{gathered}[/tex]The current in the circuit is I = 7 A
The number of electrons in 1 m^3 is
[tex]\begin{gathered} n\text{ = 3}\times\text{6.03}\times10^{28}\text{ } \\ =1.809\times10^{29}\text{ } \end{gathered}[/tex]So the number of electrons in the entire wire will be
[tex]\begin{gathered} N=\pi r^2l\times n \\ =3.14\times(2.59\times10^{-3})^2\times12.192\times1.809\times10^{29} \\ =4.65\times10^{25} \end{gathered}[/tex]Let the time taken by the current to flow along the length of the wire be t.
The total time taken will be 2t.
The time can be calculated by the formula
[tex]t=\frac{ne}{I}[/tex]Here, e = 1.6 x 10^(-19) C is the charge of electron.
Substituting the values, the time will be
[tex]\begin{gathered} t=\frac{4.65\times10^{25}\times1.6\times10^{-19}}{7} \\ =\text{ 1.063 }\times10^6\text{ s} \end{gathered}[/tex]The total time will be
[tex]\begin{gathered} 2t=\text{ 2}\times1.063\times10^6 \\ =2.125\text{ }\times10^6\text{ s} \end{gathered}[/tex]
