Current Electricity 1 Question 11

11. Drift speed of electrons, when 1.5A of current flows in a copper wire of cross-section 5mm2 is v. If the electron density in copper is 9×1028/m3, the value of v in mm/s is close to (Take, charge of electron to be =1.6×1019C )

(201 9Main, 9 Jan I)

(a) 0.02

(b) 0.2

(c) 2

(d) 3

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Solution:

  1. Relation between current (I) flowing through a conducting wire and drift velocity of electrons (vd) is given as

I=neAvd

where, n is the electron density and A is the area of cross-section of wire.

vd=IneA

Substituting the given values, we get

or

v=1.59×1028×1.6×1019×5×106v=1.5×10372m/s=0.2×104m/sv=0.02mm/s



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