A copper wire has a cross sectional area of $1 m m^{2}$ . The electron density of copper is $8.5 \times 10^{28} m^{3}$ . Calculate the mean drift velocity of the electrons through the wire when the current is 3 A.

Q. There are

8.4 \times 10^{22}

free electrons per

c m^{3}

in copper, the current in the wire is

0.21 A

(

e = 1.6 \times 10^{- 19} C

). Then the drifts velocity of electrons in a copper wire of

1 m m^{2}

cross section will be:-

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A uniform wire of length 2.0m and cross-sectional area 10−7m2 carries a current of 1.6A. If there are 1028 free electrons per m3 in copper, the drift speed of electrons in copper is

The correct option is B 10mm/sVd=IneA=1.61028×10−7×1.6×10−19=10191028×10−7=1100m/sec=10mm/sec

A uniform wire of length $2.0 m$ and cross-sectional area $10^{- 7} m^{2}$ carries a current of $1.6 A$ . If there are $10^{28}$ free electrons per $m^{3}$ in copper, the drift speed of electrons in copper is

The correct option is B $10 m m / s$
$V_{d} = \frac{I}{n e A} = \frac{1.6}{10^{28} \times 10^{- 7} \times 1.6 \times 10^{- 19}} = \frac{10^{19}}{10^{28} \times 10^{- 7}} = \frac{1}{100} m / s e c = 10 m m / s e c$