Answer:
Current density [tex]j=1.44\times 10^7A/m^2[/tex]
Electron density [tex]=5.55\times 10^{18}electron/sec[/tex]
Explanation:
We have given power = 100 watt
Current = 0.89 A
Diameter d = 0.280 mm
So radius [tex]r=\frac{d}{2}=\frac{0.28}{2}=0.14mm=0.14\times 10^{-3}m[/tex]
Area [tex]A=\pi r^2=3.14\times (0.14\times 10^{-3})^2=0.016\times 10^{-6}m^2[/tex]
We know that current density [tex]J=\frac{I}{A}=\frac{0.89}{0.016\times 10^{-6}}=1.44\times 10^7A/m^2[/tex]
Now we have to calculate the electron density
We have current i = 0.89 A = 0.89 J/sec
Charge on 1 electron [tex]1.6\times 10^{-19}C/electron[/tex]
So electron density [tex]=\frac{0.89j/sec}{1.6\times 10^{-19}C/electron}=5.55\times 10^{18}electron/sec[/tex]
