A current i in a circular loop of radius b produces magnetic field. At a fixed point far from the loop (on its axis) the magnetic field is proportional to which of the following combinations of i and b?
A
ib
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B
ib2
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C
i2b
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D
i/b2
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Solution
The correct option is Aib2 The magnetic field on the axis at a distance a from the center of a current carrying circular loop of radius b is, Baxis=μ0ib2(b2+a2)32 Given, a>>b ∴Baxis=μ0ib2a3(1+a2b2)32=μ0ib2a3 where we have neglected a2b2 in comparison to 1, ∴Baxis∝ib2