# Help involving vector (bio-savart law)

URGENT help involving vector (bio-savart law)

Hi, I have an exam monday and normally have no problems finding the components of integration, however in this one I don't know why but I do. Current is flowing in the loop in the direction shown, and a is the radius of the loop. The magnetic field from the y-components cancel out, so all that there is is the x component. To find the x component I thought it is $$\int$$ dbx/r...but according to my textbook and an old exam it is $$\int$$ dba/r...I have been trying to figure out the logic behind this but I cannot figure it out, we did a problem like this in class and the teacher did it my way....can someone help please?

#### Attachments

• e&m.JPG
8.7 KB · Views: 342

Anybody, please? It's a final and if I don't get this cleared up I'm gonna be really confused :S

tiny-tim
… To find the x component I thought it is $$\int$$ dbx/r...but according to my textbook and an old exam it is $$\int$$ dba/r...