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NEET PHYSICSEasy

The unit of specific resistance is:

A

Ohm / cm2^2

B

Ohm / cm

C

Ohm cm

D

(Ohm cm)−1^{-1}

Step-by-Step Solution

  1. Definition: Specific resistance (or resistivity, denoted by ρ\rho) is defined by the relationship between the resistance (RR) of a conductor, its length (ll), and its cross-sectional area (AA): R=ρlAR = \rho \frac{l}{A} .
  2. Rearrangement: To find the unit of ρ\rho, rearrange the formula: ρ=RAl\rho = R \frac{A}{l}.
  3. Dimensional Analysis:
  • The unit of Resistance (RR) is Ohm (Ω\Omega).
  • The unit of Area (AA) in the CGS system is cm2^2.
  • The unit of Length (ll) is cm.
  1. Calculation: Substituting these units gives: Unit of ρ=Ohm×cm2cm=Ohm⋅cm\text{Unit of } \rho = \frac{\text{Ohm} \times \text{cm}^2}{\text{cm}} = \text{Ohm} \cdot \text{cm}
  2. Note: The SI unit is Ohm metre (Ω\Omega m), but Ohm centimetre (Ω\Omega cm) is a commonly used submultiple .
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