Give two examples of drift velocity

Solved question 1: what is the drift velocity of electrons in a copper wire of cross-sectional area 1.5 mm2 when a 3A is flowing through it?( n = 8.5 x 1028 /m3)
Solution: Vd = I/nAq
Area = 1.5 mm2 = 1.5 × (10-3)2 ; q = 1.6 ×10-19 C
Drift velocity = 3 / 8.5 × 1028 ×1.5×10-6×1.6 ×10-19
= 0.147×10-3
= 1.47×10-3 m/s
Solved question 2: The drift velocity of a free electron in a conductor carrying a current I is v, when the cross-sectional area of the conductor is r. Find the current in another conductor of same material with half the radius when the drift velocity of the electron is 3v?
Solution: We know that I = nAqVd
Let the current i in the first conductor be = nπr2qVd
The current in the second conductor = nπ(r/2)2q.3Vd
= 3/4(nπr2qVd)

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