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Physics NCERT Exemplar Solutions Class 11th Chapter Fifteen Magnetic Field due to a Current Element Physics Moving Charges and Magnetism Physics Class 12th

Magnetic fields at two points on the axis of a circular coil at a distance of 0.05m 0.2m from the centre are in the ratio 8 : 1. The radius of coil is-------------.

Option 1 -

0.15m

Option 2 -

1.0m

Option 3 -

0.1m

Option 4 -

0.2m

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Answered by

Vishal Baghel | Contributor-Level 10

2 months ago

Correct Option - 3

Detailed Solution:

Magnetic field on the axis of a circular coil at distance x from centre, B = $\frac{μ_{0} N i r^{2}}{2 {(r^{2} + x^{2})}^{\frac{3}{2}}}$ $\frac{_{}^{}}{{^{}^{}}^{\frac{}{}}}$

$\frac{{(r^{2} + {(0.2)}^{2})}^{\frac{3}{2}}}{{(r^{2} + {(0.05)}^{2})}^{\frac{3}{2}}} = 8$ $\frac{r^{2} + {(0.2)}^{2}}{r^{2} + {(0.05)}^{2}} = 4 \Rightarrow r^{2} = 0.01 \Rightarrow r = 0.1 m .$

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Magnetic fields at two points on the axis of a circular coil at a distance of 0.05m 0.2m from the centre are in the ratio 8 : 1. The radius of coil is-------------.

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