ANSWERS: 1

Hi Prabhu, You need to know the formula for drift velocity I=nAeV Where I is the current through the wire,A is the area of crosssection of the wire e is the charge of electron i.e 1.6 x 10^19 columbs Finally V is the velocity of drift =I/nAe Here n= number of electrons=1.4x10^21 A=pi x(4x10^3)^2 = pi x 16 x 10 ^6 sq mts = 5 x 10 5 sq mts approx now substituting the values in the formula we get, V= 7.48/[(1.6x10^19)*(5 x 10 5)*(1.4x10^21)] => V= 7.48/1.12 x10^2 = 6.96 x 10^2 = 696mts/ sec which is too high for electron drift speed.Drift speed is of the order 10^2 May be the data provided is just for calculation purpose.Though drift speed electrons take more than an hour to travel one meter but,con't confuse it with the speed of electricity.That's different. Have any question,please ask.
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