WBJEE · Physics · Magnetic Effects of Current
The ratio of magnetic field and magnetic moment at the centre of a current carrying circular loop is \(x\). When both the current and radius is doubled the ratio will be
- A \(x / 8\)
- B \(x / 4\)
- C \(x / 2\)
- D \(2 x\)
Answer & Solution
Correct Answer
(A) \(x / 8\)
Step-by-step Solution
Detailed explanation
\[ \begin{aligned} & \text { Hints: } \mathrm{B}=\frac{\mu_0 \mathrm{I}}{2 a} \quad \quad \mathrm{M}=\mathrm{I}\left(\pi a^2\right) \\ & \frac{\mathrm{B}}{\mathrm{M}}=\frac{\mu_0 \mathrm{I}}{2 a} \times \frac{1}{\mathrm{I} \pi a^2}=\frac{\mu_0}{2 \pi a^3}=x \end{aligned} \]…
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