This question was previously asked in

NDA (Held On: 19 April 2015) General Ability Test Previous Year paper

Option 3 : Is the same for all conductors

Electric charges and coulomb's law (Basic)

42773

10 Questions
10 Marks
10 Mins

__CONCEPT__:

Resistivity is an inverse of conductivity i.e.

ρ = 1/σ

Where ρ = resistivity, σ = conductivity

ρ × σ = 1 = constant

__EXPLANATION__:

**Conductivity**is the measure of the**ease at which an electric charge or heat can pass through a material**- The material which has high conductivity is called conductor and which has very low conductivity is called non-conductor
- Metal has high conductivity and non-metal has very low conductivity
- It is also known as specific conductance
- It is an intrinsic property of a material

**Resistivity:**Resistivity is the resistance per unit length and cross-sectional area- It is the
**property of the material that opposes the flow of charge or the flow of electric current** - The unit of resistivity is an ohmmeter
- A material with high resistivity means it has got high resistance and will resist the flow of electrons
- A material with low resistivity means it has low resistance and thus the electrons flow smoothly through the material

- It is the
- The material which has a low value of resistivity is a good conductor

Hence the **product of resistivity and conductivity of a metal is always constant (equal to 1). **So option 3 is correct.