What's the difference? Is Ampere's law a special case (when the conductor carrying the current is a straight wire?)
OK, thanks. Btw, isn't the last calculation wrong here: http://planetphysics.org/encyclopedia/QuarterLoopExampleOfBiotSavartLaw.htmlBiot-Savart law is the more important and fundamental one. Ampere's law can be derived from it but can only be used in some very specific situations, but not only in straight wire cases. It can be applied to sheets of current, solenoids, etc.