Two wires of the same length and material have a diameter of wire A twice that of wire B. If the resistance of wire B is R then the resistance of wire A is

  1. R/4
  2. R/2
  3. R
  4. 4R


Two wires of the same length and material have a diameter of wire A twice that of wire B. If the resistance of wire B is R then the resistance of wire A is

Two wires of the same length and material have a diameter of wire A twice that of wire B. If the resistance of wire B is R then the resistance of wire A is R/4.

  1. the resistance of the wire is given by R = ρ*L/A
  2. because both wires have the same length and the same material so the value of ρ same for both wires.
  3. The cross-sectional area of the wire is A = πr2
  4. first wire: RA = ρ*L/πr2 = ρ*L/4πD2/4  because r = D/2 (put D = 2D because wire A have double diameter)
  5. second wire: RB = ρ*L/πr2 = ρ*L/πD2/4  because r = D/2
  6. divide RA and RB i-e RA/RB = 1/4
  7. RA = RB/4

This question is about MSc Electricity and Magnetism MCQs. This is the previous year’s question about the competitive exams.


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