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JAMB Physics 2007 Question 22

Question 22

Current Electricity

A conductor has a diagram of 1.00 mm and length 2.00 m. If the resistance of the material 0.1Ω, its resistivity is

  1. A.3.93 × 10−8 Ωm.
  2. B.3.93 × 10−6 Ωm.
  3. C.2.55 × 102 Ωm.
  4. D.2.55 × 105 Ωm.
Show the answer and explanation

Answer: A (3.93 × 10−8 Ωm.)

Explanation

Cross-section A = πd2/4 = π(1.0 × 10−3)2/4 = 7.85 × 10−7 m2. ρ = RA/L = 0.1 × 7.85 × 10−7 ÷ 2 = 3.93 × 10−8 Ω m.