JEE Advanced · Physics · 21. EMI
A circular wire loop of radius \(R\) is placed in the \(x-y\) plane centered at the origin \(O\). A square loop of side \(a(a< < R)\) having two turns is placed with its centre at \(z=\sqrt{3} R\) along the axis of the circular wire loop, as shown in figure.

The plane of the square loop makes an angle of \(45^{\circ}\) with respect to the \(z\)-axis. If the mutual inductance between the loops is given by \(\frac{\mu_{0} a^{2}}{2^{p / 2} R}\), then the value of \(p\) is
- A 2
- B 3
- C 5
- D 7
Answer & Solution
Correct Answer
(D) 7
Step-by-step Solution
Detailed explanation
The magnetic field due to current carrying wire at the location of square loop is
\(B=\frac{\mu_{0}}{4 \pi} \frac{2 \pi i R^{2}}{\left(R^{2}+3 R^{2}\right)^{3 / 2}}=\frac{\mu_{0} i}{16 R}\)
The mutual induction
\(\begin{array}{l}
M=\frac{N \phi}{i}=\frac{2}{i}\left[\frac{\mu_{0} i}{16 R} \times a^{2} \cos 45^{\circ}\right] \\
\therefore \quad M=\frac{\mu_{0} a^{2}}{2^{\frac{7}{2}} R}
\end{array}\)
\(B=\frac{\mu_{0}}{4 \pi} \frac{2 \pi i R^{2}}{\left(R^{2}+3 R^{2}\right)^{3 / 2}}=\frac{\mu_{0} i}{16 R}\)
The mutual induction
\(\begin{array}{l}
M=\frac{N \phi}{i}=\frac{2}{i}\left[\frac{\mu_{0} i}{16 R} \times a^{2} \cos 45^{\circ}\right] \\
\therefore \quad M=\frac{\mu_{0} a^{2}}{2^{\frac{7}{2}} R}
\end{array}\)
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