The resistivity of a conductor in which a current density of $3.5\, A\, m^{-2}$ is found to exist on applying an electric field of $28\, V\, m^{-1}$ will be

8 Ω m

The correct answer is Option (3) → 8 Ω m

Given:

Current density, $J = 3.5\ \text{A·m}^{-2}$

Electric field, $E = 28\ \text{V·m}^{-1}$

Relation between $E$, $J$, and resistivity $ρ$:

$E = ρJ$

∴ $ρ = \frac{E}{J}$

$ρ = \frac{28}{3.5} = 8\ \Omega\text{·m}$

Answer: $ρ = 8\ \Omega\text{·m}$