First slide
Magnetism
Question

Two short bar magnets of length 1cm each have magnetic moments 1.20 Am2 and 1.00 Am2, 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 20.0cm. The value of the resultant horizontal magnetic induction at the mid-point O of the line joining their centers is close to (horizontal component of earth’s magnetic induction is 3.6×105Wb/m2)

Moderate
Solution

The situation is as shown in the figure. As the point O lies on broad side position with respect to both the magnets. Therefore, 

The net magnetic field at point O is 
Bnet=B1+B2+BH 
Bnet=μ04πM1r3+μ04πM2r3+BH=μ04πr3(M1+M2)+BH 
Substituting the given values, we get 

Bnet =4π×1074π×10×1023[1.2+1]+3.6×105=107103×2.2+3.6×105=2.2×104+0.36×104=2.2×104+0.36×104=2.56×104Wb/m2
 

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