Answer:
c) 10 microns/s
Explanation:
The drift velocity (the velocity of the current) of the electrons in a wire is given by
[tex]v=\frac{I}{nAq}[/tex]
where
I is the current
n is the electron number density (the number of electrons per unit volume)
A is the cross-sectional area of the wire
[tex]q=1.6\cdot 10^{-19} C[/tex] is the charge of one electron
Taking a current of
I = 1 A
in a wire of radius r = 1 mm (0.001 m), so with cross-sectional area
[tex]A=\pi r^2 = \pi (0.001 m)^2=3.14\cdot 10^{-6} m^2[/tex]
made of copper, whose electron density number is around
[tex]n=8.5\cdot 10^{28} m^{-3}[/tex]
we find
[tex]v=\frac{1 A}{(8.5\cdot 10^{28} m^{-3})(3.14\cdot 10^{-6} m^2)(1.6\cdot 10^{-19} C)}=2.34\cdot 10^{-5} m/s[/tex]
which means that the closest estimate is
c) 10 microns/s
