A copper wire of cross-sectional area $1.0 imes 10^{-7}\ ext{m}^2$…

Question

A copper wire of cross-sectional area $1.0 	imes 10^{-7}\ 	ext{m}^2$ carries a current of 1.5 A. The free-electron number density is $8.5 	imes 10^{28}\ 	ext{m}^{-3}$ and $e = 1.6 	imes 10^{-19}\ 	ext{C}$. The drift speed of the electrons is approximately

Accepted Answer

A. $1.1 	imes 10^{-3}\ 	ext{m s}^{-1}$

1. Use $v_d = I/(neA)$.
2. Denominator: $neA = 8.5	imes10^{28} 	imes 1.6	imes10^{-19} 	imes 1.0	imes10^{-7} = 1.36	imes10^{3}$.
3. $v_d = 1.5/1.36	imes10^{3} \approx 1.1	imes10^{-3}\ 	ext{m s}^{-1}$ (about 1.1 mm/s).
4. B inverts the magnitude; D is the speed of light, not drift speed.
_Source: NCERT Class 12 Physics Ch 3 "Current Electricity", p.6_

Answer

$1.1 	imes 10^{3}\ 	ext{m s}^{-1}$

Answer

$8.5 	imes 10^{-2}\ 	ext{m s}^{-1}$

Answer

$3.0 	imes 10^{8}\ 	ext{m s}^{-1}$

A copper wire of cross-sectional area $1.0 \times 10^{-7}\ \text{m}^2$ carries a current of 1.5 A. The free-electron number density is $8.5 \times 10^{28}\ \text{m}^{-3}$ and $e = 1.6 \times 10^{-19}\ \text{C}$. The drift speed of the electrons is approximately