- $I_{enc} = \frac{Ir^2}{R^2}$
- $\oint \vec{B} . {dl} = \oint B r d \phi$
- $= B r \oint d \phi = B r . 2 \pi$
- $B . r . 2 \pi =\mu_0 I_{enc} = \frac{\mu_0 I r^2}{R^2}$
- $B = \frac{\mu_0 I r^2}{R^2} \times \frac{1}{2 \pi r} = \frac{\mu_0 I r}{2 \pi R^2}$
![image](https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/physics-class-12-unit-04-chapter-02-generalization-of-amperes-law-and-its-applications-l-2_7-bhcxkuxznrs-12.jpg)