Two short bar magnets of length 1 cm each have magnetic moments 1 .20   A   m 2 and 1 .00   A…

Two short bar magnets of length 1cm each have magnetic moments 1.20 A m2 and 1.00 A m2 respectively. They are placed on a horizontal table parallel to each other with their N poles pointing towards the south. They have a common magnetic equator and are separated by a distance of 20.0 cm. The value of the resultant horizontal magnetic induction at the mid-point O of the line joining their centres is close to
( Horizontal component of earth's magnetic induction is 3.6×10-5  Wb m-2 )
  1. 3.50×10-4 Wb m-2
  2. 5.80×10-4  Wb m-2
  3. 3.6×10-5  Wb m-2
  4. 2.56×10-4 Wb m-2

Solution



B net = B 1 + B 2 + B H

= μ 0 4 π M 1 x 3 + μ 0 4 π M 2 x 3 + B H

= { 10 −7 ( 1.2+1 ) } ( 0.1 ) 3 +3.6× 10 −5

= 2.56 × 10 - 4  Wb / m 2

Asked in: JEE Main 2013 (07 Apr)

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