Question

there are 10^28 free electrons per c.c. in a copper conductor and all of which contribute to a current of 1.0 A in a copper wire 10^-6 cm^2 area of cross section. calculate the average speed of electrons in copper

Answer 1

answer in attachment

Answer 2

Answer:  

The average speed of ‘electrons in copper’ is 625 m/s.

Solution:

The given data’s are

Number of electrons per cc in copper $\bold{=10^{28}}$ = density of charge carriers

Current I = 1 A

Cross section Area $\bold{=10^{-6} \mathrm{cm}^{2}}$.

The average speed of the electrons is the ‘drift velocity’ of the electrons in a sample. Drift velocity is the ‘average velocity’ attained by charge carriers in a material when electric current is passed. The formula for drift velocity is

$\bold{v_{d}=\frac{I}{n q A}}$

Here, I is the current passed in the material, n is the density of charge carriers in the material, q is the magnitude of charge and A is the cross section area of the material exposed to electric field.

$v_{d}=\frac{1}{10^{28} \times 1.6 \times 10^{-19} \times 10^{-6}}=\frac{1}{1.6 \times 10^{3}}$

$v_{d}=\frac{1000}{1.6}=625\ \mathrm{m} / \mathrm{s}$