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A material ' B ' has twice the specific resistance of ' A '. A circular wire made of ' B ' has twice the diameter of a wire made of ' A '. Then for the two wires to have the same resistance, the ratio _A / _B of their respective lengths must be

Options

  1. A2
  2. B1
  3. C1 2
  4. D1 4

Correct answer

A. 2

Step-by-step solution

R ₁= _ A _ A R _ A ^2 R ₂= _ B _ B R _ B ^2 _ A _ B = _ B R _ A ^2 _ A R _ B ^2 = 2 _ A R _ A ^2 _ A 4 R _ A ^2 _ B _ A =2

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