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Some of the characterising parameters of a materials are:
1. magnetic permeability
2. electron relaxation time
3. electron effective mass
4. energy band gap
In case of metals, increase in one of the above parameters decreases its conductivity, while increase in another
increases the conductivity. These two parameters are respectively:
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- 1 and 3
- 3 and 2
- 4 and 3
- 1 and 2
Correct Option: B
Conductivity is given by relation
| σ = | = | ||
| 2m | ρ |
where, n = no. of free electrons
e = charge of electron
τ = relaxation time
m = mass of electron
ρ = resistivity of metal
σ = conductivity of metal
From above relation we conclude that conductivity increases on increasing relaxation time while conductivity decreases on increasing effective mass.
