Biot Savart law (vector form) | Moving charges & magnetism | Khan Academy
Channel: Khan Academy India - English
Date: 2021-03-19

Biot Savart law states that the magnetic field due to a tiny current element at any point is proportional to the length of the current element, the current, the sine of the angle between the current direction and the line joining the current element and the point, and inversely proportional to the square of the distance of that point. 
The direction of the magnetic field is in the direction of dl cross r. You can also use the right hand clasp rule to figure out the direction. 

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Created by Mahesh Shenoy