Write equation of magnetic field due to a circular current carrying loop at a point on the axis of the loop. Give its special cases.

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Magnetic field $\overrightarrow{\mathrm{B}}$ due to I current carrying wire with $\mathrm{R}$ radius at a $x$ distance is given by, $B=\frac{\mu_{0} I R^{2}}{2\left(x^{2}+R^{2}\right)^{3 / 2}}$

Case $1:$

When number of turns are $\mathrm{N}$, then magnetic field is $\mathrm{B}=\frac{\mu_{0} \mathrm{NIR}^{2}}{2\left(x^{2}+\mathrm{R}^{2}\right)^{3 / 2}}$

Case $2:$

Magnetic field at centre with $\mathrm{N}$ turn $\mathrm{B}=\frac{\mu_{0} \mathrm{NI}}{2 \mathrm{R}}$

Case $3$ :

When $x>>\mathrm{R}$, then $\mathrm{B}=\frac{\mu_{0} \mathrm{NIR}^{2}}{2 x^{3}}$

Case $4$ :

At $x=\mathrm{R}$ distance from centre,

$B=\frac{\mu_{0} N I R^{2}}{2\left(R^{2}+R^{2}\right)^{3 / 2}}=\frac{\mu_{0} N I}{2^{5 / 2} R}$

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