Question

5. Obtain electron concentration, mobility and drift velocity in a metal for the following data: Length = 5 m, Resistivity = 2.7 ×10-8 ohm-m, R = 6×10-2 ohm, I = 15 Amp,
Atomic weight = 26.98×10-3 kg/mol, Valency = 3, Density = 2.7×103 kg/m3.

Answer 1

Answer:

Given : Current I=1.5A

Cross-sectional area A=1×10

−7

m

2

Atomic mass of copper m=63.5 amu

∴ Molar mass of copper M=63.5g=63.5×10

−3

kg

Number of copper atoms per unit volume

N=ρ

M

N

A

=9×10

3

×

63.5×10

−3

6.023×10

23

=8.54×10

28

As one copper atom contributes to one conduction electron.

⟹ Number of conduction electrons per unit volume n=N=8.54×10

28

Using I=AneV

d

where V

d

is the drift velocity

∴ 1.5=10

−7

×8.54×10

28

×1.6×10

−19

×V

d

⟹ V

d

=1.1×10

−3

ms

−1