CBSE Class 12 Physics 2014 Outside Delhi Set 2 Paper

Question : 5

Total: 9

Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area 2.5×10−7m2 carrying a current of 1.8A. Assume the density of conduction electrons to be 9×1028 m−3.

Solution:

Given: ‌‌ Current (l)=1.8A
Charge density (n)=9×1028m−3
Cross-section area (A)=2.5×10−7m2
Charge of electron (q)=1.6×10−19C
vd‌=‌

nAq

.
‌=‌

1.8

9×1028×2.5×10−7×1.6×10−19

‌=0.0005m∕ s
‌=0.5‌mm‌ s−1

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