The unit of conductivity (K) is:

The correct answer is Option (2) → Ω⁻¹ m⁻¹

Conductivity is the reciprocal of resistivity: κ = 1/ρ. Resistivity has the unit Ω m, so

    unit of κ = 1/(Ω m) = Ω⁻¹ m⁻¹ = S m⁻¹

(1 S = 1 Ω⁻¹). The SI unit of conductivity is S m⁻¹; it is often also written as S cm⁻¹.

Why the other options are incorrect

• Option (1) Ω m — Incorrect. The unit of resistivity, the reciprocal of conductivity.

• Option (3) Ω m⁻¹ — Incorrect. Has resistance in the numerator; conductivity must have Ω⁻¹.

• Option (4) 2Ω m⁻¹ — Incorrect. A numerical factor is not part of a unit, and Ω again has the wrong sign of power.

NCERT (2026-27 edition):
Conductance of Electrolytic Solutions – “… The SI units of conductivity are S m⁻¹ but quite often, κ is expressed in S cm⁻¹. Conductivity of a material in S m⁻¹ is its conductance when it is 1 m long and its area of cross section is 1 m².”