Correct Answer - Option 4 : 0.01 mm per sec
Concept:
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Drift Velocity: The average speed of electrons by which they slowly move inside a conductor under influence of an applied electric field is called drift velocity.
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Drift velocity of the electrons is calculated by:
\(v_d=\frac{I}{neA}\)
I is current in the conductor, e is the electronic charge, n is the number of free electrons per unit volume A is cross-sectional Area.
Calculation:
Given,
The number of free electrons per unit volume n = 8.4 × 10 22 / cm 3
Current I = 1.344 A
Cross-sectional Area A = 1 mm2 = 10 -2 cm 2
Electronic charge e = 1.602 × 10 -19 C
Drift velocity from the above expression will be
\(v_d = \frac{1.344}{(8.4 \times 10^{22})(1.6 \times 10^{-19})(10^{-2})}\)
⇒ vd = 10 -2 cm / sec
1 cm = 10 mm
So drift velocity (mm /sec) is
vd = 10 -1 mm / sec
So, correct option is 0.1 mm per sec