CBSE Class 12 Physics 2014 Outside Delhi Set 1 Paper

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Question : 14
Total: 30
Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area 1.0×107m2 carrying a current of 1.5A. Assume the density of conduction electrons to be 9×1028 m3.
Solution:  

vd=
I
nAq
, where

I is the current
n is charge density
q is the charge of electron and
A is the cross sectional area
vd=
1.5
9×1028×1.0×107×1.6×1019

vd=10.4×104m sec
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