(a) 
(b) 
(c) 
(d) 
Correct Answer: (a)
Explanation
Metals have very high conductivity due to abundant
free electrons.
Notes for
More Information
Electrical
Conductivity of Metals
1. Electrical conductivity (σ) indicates
how easily a material allows electric current to flow.
2. Metals have very high electrical conductivity because
they contain a large number of free electrons.
3. These free electrons can move easily under an electric field, allowing
current to flow.
Typical
Value of Conductivity of Metals
4. The electrical conductivity of metals is typically of the order of:
5. Good conductors like silver, copper, and gold have
conductivity values in the range of:
6. Hence, the closest order of magnitude for the
conductivity of metals is:
· Option (a)
Why Metals
Have High Conductivity
7. In metals, valence electrons are loosely bound to
atoms.
8. These electrons form a “sea of free electrons”.
9. Because of this, electrons can move freely when a voltage is applied.
10.
This results in high electrical
conductivity.
Comparison
with Other Materials
11.
Metals (good conductors):
12.
Semiconductors / poor
conductors:
13.
Insulators:
Additional
Information
14.
Resistivity (ρ) is defined as the resistance of a conductor of:
·
Unit length
·
Unit cross-sectional area
15.
The unit of resistivity is ohm-meter (Ω·m).
16.
Higher resistivity means a poorer conductor.
17.
Conductivity (σ) is the reciprocal of resistivity:
18.
The unit of conductivity is ohm⁻¹ m⁻¹ or Siemens
per meter (S/m).
Energy Band
Explanation
19.
In conductors (metals):
·
The valence band overlaps the conduction
band.
·
Electrons move freely → high conductivity.
20.
In semiconductors:
·
There is a small energy gap between
valence and conduction bands.
·
Conductivity increases with temperature or doping.
21.
In insulators:
·
There is a large energy gap.
·
Electrons cannot move easily → very low
conductivity.
Semiconductor
Conductivity
22.
Semiconductors generally have conductivity in the
range:
23.
Intrinsic semiconductors have conductivity of the order of:
Final
Answer
24.
The electrical conductivity of metals is of the
order of:
25.
Therefore, option (a) is the
correct answer.