The earth’s magnetic field at a given point is $0.5 \times {10^{ - 5}}\,Wb{\rm{ - }}{m^{ - 2}}$. This field is to be annulled by magnetic induction at the center of a circular conducting loop of radius $5.0\,cm$. The current required to be flown in the loop is nearly......$A$
AIIMS 2003, Medium
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(b) Magnetic field at the centre of circular loop
$B = \frac{{{\mu _0}}}{{4\pi }}\frac{{2\pi i}}{r} $
$B = \frac{{{\mu _0}}}{{4\pi }}\frac{{2\pi i}}{r} $
$\Rightarrow 0.5 \times {10^{ - 5}} = \frac{{{{10}^{ - 7}} \times 2 \times 3.14 \times i}}{{5 \times {{10}^{ - 2}}}}$
$i = 0.4 \,A$
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