As only the outer surface of the sphere is charged, consider the element as a ring, as shown in the figure.
![](https://www.sarthaks.com/?qa=blob&qa_blobid=645167295175896251)
The equivalent current due to the ring element,
![](https://www.sarthaks.com/?qa=blob&qa_blobid=6498625829898953867)
and magnetic induction due to this loop element at the centre of the sphere, O,
![](https://www.sarthaks.com/?qa=blob&qa_blobid=16053275088856883011)
using above equation
![](https://www.sarthaks.com/?qa=blob&qa_blobid=17834612240879200831)
Hence, the total magnetic induction due to the sphere at the centre, O,
![](https://www.sarthaks.com/?qa=blob&qa_blobid=1791696637089423568)