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JAMB Physics 2014 Question 37

Question 37

Current Electricity

If a metal wire 4 m long and cross-sectional area 0.8 mm2 has a resistance of 6Ω, find the resistivity of the wire.

  1. A.3.0 × 10−5Ωm.
  2. B.1.2 × 10−6Ωm.
  3. C.3.2 × 10−6Ωm.
  4. D.5.3 × 10−7Ωm.
Show the answer and explanation

Answer: B (1.2 × 10−6Ωm.)

Explanation

A = 0.8 mm2 = 0.8 × 10−6 m2. ρ = RA/L = 6 × 0.8 × 10−6 ÷ 4 = 1.2 × 10−6 Ω m.