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JEE Main202127 Aug 2021Evening ShiftPhysicsMagnetic Effects of CurrentActual

A coaxial cable consists of an inner wire of radius a surrounded by an outer shell of inner and outer radii b and c respectively. The inner wire carries an electric current i 0 which is distributed uniformly across cross-sectional area. The outer shell carries an equal current in opposite direction and distributed uniformly. What will be the ratio of the magnetic field at a distance x from the axis when i x < a a

Options

  1. Aa 2 x 2
  2. Bb 2 - a 2 x 2
  3. Cx 2 b 2 - a 2
  4. Dx 2 a 2

Correct answer

D. x 2 a 2

Step-by-step solution

B 1 × 2 π x = μ 0 I 0 ( x ) 2 a 2 B 2 × 2 π x = μ 0 I 0 B 1 B 2 = x 2 a 2

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