Multiple choice

If the resistance of a wire is 30 Ω with a length of 3 m and diameter of 0.4 mm, then calculate the resistivity of the wire.

  1. 11.25 x 10-6 Ωm

  2. 1.25 x 10-6 Ωm

  3. 80 x 106 Ωm

  4. 0.0125 x 10-6 Ωm

  5. 0.0013 x 10-6 Ωm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

R = 30 Ω, l = 3 m, diameter = 0.4 mm, radius = 0.2 mm = 0.2 x 10-3 m Area = πr2 = 3.14 x (0.2 x 10-3)2 = 0.125 x 10-6 m2 ρ = RA/l = 30 x 0.125 x 10-6/3 = 1.25 x 10-6 Ωm  

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