Question

The number density of free electrons in a copper conductor is estimated at `8.5 xx 10^(28) m^(-3)`. How long does an electron take to drift from one end of a wire 3.0 m long to its other end? The area of cross-section of the wire is `2.0 xx 10^(-6)m^(2)` and it is carrying a current of 3.0A.

Answer 1

Here, `n = 8.5 xx 10^(28)m^(-3) , l = 3.0 m , A = 2.0 xx 10^(-6) m^(2) , I = 3.0A, t = ?`
As, `I= n Ae v_(d) :. V_(d)= I/(nAe)`,
Now, `t = l/v_(d) = (l n A e)/I = (3.0 xx 8.5 xx 10^(28) xx 2.0 xx 10^(-6) xx 1.6 xx 10^(-19))/3.0 = 2.72 xx 10^(4) s= 7` hour 33 minute.