Two concentric coils of 20 turns each are placed in same plane. Their radii are $30 \mathrm{~cm}$ and $60 \mathrm{~cm}$ and carry $0.4 \mathrm{~A}$ and $0.6 \mathrm{~A}$ currents respectively in opposite directions. The magnetic induction at the centre in tesla is ....... .

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Aicharya · Accepted Answer

As $\quad B_{	ext {centre }}=\frac{\mu_0 n I}{2 r}$ So, Magnetic field at $\mathrm{O}$, $ \begin{aligned} & B_O=\frac{\mu_0}{2}\left[\frac{n_1 I_1}{r_1}-\frac{n_2 I_2}{r_2}ight] \ & n_1=n_2=20 \ & B_O=\frac{\mu_0}{4 \pi} \cdot 2 \pi 	imes 20\left[\frac{0.4}{30 	imes 10^{-2}}-\frac{0.6}{60 	imes 10^{-2}}ight] \ & =\frac{\mu_0}{2} 	imes 20\left[\frac{0.8-0.6}{60 	imes 10^{-2}}ight]=\frac{10}{3} \mu_0 \end{aligned} $

Two concentric coils of 20 turns each are placed in same plane. Their radii are $30 \mathrm{~cm}$ and $60…

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