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  • The current density in a cylindrical wire of radius <img alt="\mathrm{r=4.0 \mathrm{~mm} \: is\: 1.0 \times 10^{6} \mathrm{~A} / \mathrm{m}^{2}}" src="https://entrancecorner.oncodecogs.com/gif.late

The current density in a cylindrical wire of radius \mathrm{r=4.0 \mathrm{~mm} \: is\: 1.0 \times 10^{6} \mathrm{~A} / \mathrm{m}^{2}}. The current through the outer portion of the wire between radial distances \mathrm{\frac{r}{2}} and \mathrm{r} is  \mathrm{x \pi A}; where \mathrm{x } is ______.

Option: 1

12


Option: 2

-


Option: 3

-


Option: 4

-


Answers (1)

best_answer

\mathrm{J= \frac{I}{A}}


\mathrm{I= \left [ J\times \left [ \pi r^{2}-\frac{\pi r^{2}}{4} \right ] \right ]= J\times \frac{3 \pi r^{2}}{4}}
   \mathrm{= 1\times 10^{6}\times \frac{3}{4}\times \pi \times 16\times 10^{-6}}
    \mathrm{= 12 \pi}

The answer is 12

Posted by

Irshad Anwar

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