Biot–Savart law and Ampere's law

[minifhncc]

Hello,

Just a quick question... in which cases do I use the Biot–Savart law and Ampere's law? ie. in what cases is it easier to calculate the magnetic field with the laws?

Thanks

 

[stevenb]

Hello,

Just a quick question... in which cases do I use the Biot–Savart law and Ampere's law? ie. in what cases is it easier to calculate the magnetic field with the laws?

Thanks

Usually Biot Savart is more useful, but there are exceptions. The famous example is the infinitely long and straight wire with constant current. Here, Ampere's law is trivial to apply and easier than Biot Savart, although Biot Savart also works well and is not difficult to apply, in that case. Basically, Ampere's law requires a certain symmetry to be useful, but when you have that symmetry, the application is trivial, and easier than Biot Savart.