MCQ practice · SSC Physics Board questions · Chapter 11: Current Electricity
What is the unit of specific resistance?
Think it through first, then pick an option.
- a Ω m
- b Ω/m
- c (Ω m)⁻¹
- d Ω/m²
Answer and explanation
Correct answer: a Ω m
From ρ = RA/L the unit is Ω × m²/m = Ω m.
Why the other options are wrong
- b Ω/m: Ω/m is not the unit; ρ = RA/L divides by length but also multiplies by area. The unit is Ω m.
- c (Ω m)⁻¹: (Ω m)⁻¹ is the unit of the conductivity σ, not of the specific resistance.
- d Ω/m²: Not Ω/m²; in ρ = RA/L the area is multiplied, not divided. The unit is Ω m.
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