If we take current carrying straight wire of length, say l, and we want to find magnetic field at point p.

Using Ampere circuital law along circle(perpendicular to wire and centre lying on the wire), the circulation of magnetic field is µ_oi

Further, Magnetic field is tangential to this circle every where and also equal.

Hence implication by the law is

B(2πr)= µ_oi

B= µ_oi\(2πr)

where r à radius of circle

however if use biot savart law here then we find that

B= {µ_oi(cosφ₁-cosφ₂)}\ 4πr

Where φ₁ and φ₂ à angle between line joining point p and ends of wire

I am not able to understand what mistake I have committed in applying ampere circuital law here

Hrishant Goswami , 11 Years ago

Grade 10