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Magnetic field due to a ring having $n$ turns at a distance $x$ on its axis is proportional to (if $r$ = radius of ring)
  • A$\frac{r}{{({x^2} + {r^2})}}$
  • B$\frac{{{r^2}}}{{{{({x^2} + {r^2})}^{3/2}}}}$
  • C$\frac{{n{r^2}}}{{{{({x^2} + {r^2})}^{3/2}}}}$
  • D$\frac{{{n^2}{r^2}}}{{{{({x^2} + {r^2})}^{3/2}}}}$
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