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I studied the Maxwell laws and the Biot Savart law and I found something I cannot answer.

If you have a finite wire carrying current (let say 5m long) and you want to determine the magnetic induction vector due to it at some point that has distance r from the wire, you have 2 options I think.

If you use the Biot Savart law and you integrate over the length of the wire you get an answer which is definitely less than the answer you would get if the wire would be infinite.(B=µ

_{0}*I/(2*r*

However if you use Ampere's law for a circle around the wire (the wire is at the center of the circle and the plane of the circle is perpendicular to the line of the wire) you get that the magnetic field is B=µ

_{0}*I/(2*r*

I can't figure out why the 2 methods don't give the same result so if you could help me out please do so. It would be really appreciated.

Thanks,

Istvan