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Question 13

The number density of free electrons in a copper conductor estimated in Example 3.1 is 8.5 x 1028 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 x 10-6 m2 and it is carrying a current of 3.0 A.

Answer

Number density of free electrons in a copper conductor, n = 8.5 × 1028 m - 3 Length of the copper wire, l = 3.0 m

Area of cross-section of the wire, A = 2.0 × 10 - 6 m2

Current carried by the wire, I = 3.0 A, which is given by the relation,

I = nAeVd

Where,

e = Electric charge = 1.6 × 10 - 19 C

Vd = Drift velocity 

Therefore, the time taken by an electron to drift from one end of the wire to the other is 2.7 × 104 s.

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