Question

In copper, each atom releases one electron. If a current of 1.1A is flowing in the copper wire of diameter 1mm then the drift velocity of electrons, will approximately be (density of copper $=9\times {10}^{3}Kg{m}^{-3}$ and its atomic weight $=63)$.

• A. 10.3 mm/s
• B. 0.1 mm/s
• C. 0.2 mm/s
• D. 0.2 cm/s

Answer 1

Answer: (B)

0.1 mm/s

Electron density $n=\frac{N_A\rho }{M}=\frac{(6.023\times {10}^{23})\times (9\times {10}^3)}{63\times {10}^{-3}}=0.86\times {10}^{29}{m}^{-3}$

Drift velocity $v_d=\frac{I}{neA}=\frac{1.1}{(0.86\times {10}^{29})\times (1.6\times {10}^{-19})\times \pi (0.5\times {10}^{-3}{)}^2}=0.1\times {10}^{-3}m/s=0.1$ mm/s