Exam

JEE Main

Year

2025

Date

2 April

Shift

Morning Shift

Subject

Physics

Chapter

Magnetic Effects of Current

JEE Main 2025 · 2 April · Morning Shift · Physics · Magnetic Effects of Current

Let B_1 be the magnitude of magnetic field at center of a circular...

Let $B_1$ be the magnitude of magnetic field at center of a circular coil of radius $R$ carrying current $I$. Let $B_2$ be the magnitude of magnetic field at an axial distance ' $x$ ' from the center. For $x: R=3: 4, \frac{B_2}{B_1}$ is :

Step-by-step solution

$$\begin{aligned} & \mathrm{B}_1=\frac{\mu_0 \mathrm{i}}{2 \mathrm{R}} \qquad \mathrm{B}_2=\mathrm{B}_1 \sin ^3 \theta \\ & \therefore \frac{\mathrm{~B}_2}{\mathrm{~B}_1}=\sin ^3 \theta=\left(\frac{4}{5}\right)^3=\frac{64}{125}\end{aligned}$$