So, let's say you have a long, straight wire with a current running through it.

所以，假设你有一根很长的电线，电线是直的，有电流流过它。

So! For a long straight wire, B is equal to the magnetic constant times the enclosed current, divided by 2 pi r.

因此！对于长直导线，B 等于恒磁闭合电流的倍除以 2 pi p。

But to get a basic sense of how it works, let's return to our scenario: a circle around one long straight wire.

但是为了基本了解它是如何工作的，让我们回到我们的场景：绕一根长直线。