two loops of wire of radii 1cm and 2cm resp.are placed coaxialy .current i passes through both in same direction initialyand then the the direction of current is reversed . what is the ratio of magnetic induction at centre in first and second case

Dear darshan joshi

magnetic field at the center of loop of radius a is

B = μ i/2a

first case

B=B1 +B2

  = μi/2*1    + μ i/2*2

  = μi/2 [ 3/2]

second case

B' = B1 -B2

   =B1 +B2

  = μi/2*1    - μ i/2*2

  = μi/2 [ 1/2]

so B/B'  = 3

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