Let $B_1$ be the magnitude of magnetic field at center of a circular coil of radius $R$ carrying current $I$…
- $4: 5$
- $16: 25$
- $64: 125$
- $25: 16$
Solution

$\begin{aligned} & \mathrm{B}_1=\frac{\mu_0 \mathrm{i}}{2 \mathrm{R}} \qquad \mathrm{B}_2=\mathrm{B}_1 \sin ^3 \theta \\ & \therefore \frac{\mathrm{~B}_2}{\mathrm{~B}_1}=\sin ^3 \theta=\left(\frac{4}{5}\right)^3=\frac{64}{125}\end{aligned}$
Asked in: JEE Main 2025 (02 Apr Shift 1)
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