When a conductor of a cross-sectional area 5 x 10^-6 m2 carries a current of 6 A, the drift velocity of the conduction electrons is 1.2 x 10^-4 ms1-. What is the number density (number per unit volume) of the conduction electrons?
Correct answer: D. 6.3 x 10^28 m-3
- A. 4 x 10^-28 m-3
- B. 1.6 x 10^-27 m-3
- C. 2.5 x 10^-27 m-3
- D. 6.3 x 10^28 m-3
- E. 1.3 x 10^34 m-3
Explanation
The formula for electric current relating the drift velocity is: I = neAV Where; I = Electric current n = Number of charges per unit volume e = Electron charge A = Cross sectional area V = Drift speed Solving for 'n' : n = I/eAV Here I = 6.0 Amp e = 1.6 x 10-19 C A = 5.0 x 10-6 m2 V = 1.2 x 10^-4 m/s Put all these values inabove equation and do the calculations: n = (6.0)/ (1.6 x 10-19) (5.0 x 10-6) (1.2 x 10-4) n = 6.3 × 1028 m-3 is the answer
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