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Question
A copper wire of 10-6 m2 area of cross-section, carries a current of 2 A. If the number of electrons per cubic meter is 8 × 1028, calculate the current density and average drift velocity.
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Solution
A = 10-6 m2, I = 2A, n = 8 × 1028
Formula:
Current density, J = J = `"I"/"A"`
Drift velocity, `"V"_"d" = "J"/"ne"`
J = `"I"/"A" = 2/10^-6 = 2 xx 10^6`
J = `2xx10^6 "Am"^-2`
`"V"_"d" = "J"/"ne" = (2 xx 10^6)/(8 xx 10^28 xx 1.6 xx 10^-6)`
`"V"_"d" = = 0.1562 xx 10^-3`
`"V"_"d" = 15.6 xx 10^-5 "ms"^-1`
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