Correct Answer - Option 1 : 1.25 × 10
-3 m/s
The correct answer is option 1) i.e. 1.25 × 10-3 m/s
CONCEPT:
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Drift velocity: The average velocity attained by the electrons under the influence of an electric field is termed the drift velocity.
- The free electrons are always in a constant random motion in the conductor.
- When the conductor is connected to a battery, an electric field is generated.
- When these free electrons are subjected to an electric field, they slowly drift in the direction of the electric field applied, while maintaining the random motion.
- At this point, the net velocity of the electrons is called its drift velocity.
The drift velocity (vd) of the electron in a conductor is given by:
\(v_d =\frac{I}{nAq}\)
Where I is the current flowing through the conductor, A is the area of cross-section of the conductor, q is the charge on the electron and n is the number of electrons.
CALCULATION:
Given that:
Current, I = 20 A
Cross-sectional area of conductor, A = 10-2 cm2 = 10-6 m2
Density of electrons in the wire, n = 1029 electrons per m3
\(\Rightarrow v_d= \frac{20}{(10^{29})\;\times\;(10^{-6})\;\times\;(1.6\;\times\;10^{-19})}=1.25 \times 10^{-3}\:m/s\)