Bo, we have drawn the Amperian loop.

Bo，我们已经画出了安培环。

And, let's move clockwise around the Amperian rectangle.

然后，让我们绕着 Amperian 矩形顺时针移动。

Okay, just like we did with Gaussian surfaces, we need to look at the different sides of the Amperian rectangle.

好的， 就像我们对高斯曲面所做的那样，我们需要查看安培矩形的不同边。

Here is how we define the current inside the Amperian loop.

以下是我们如何定义安培环路内的电流。

And the integral of ds is just the length of side one of the Amperian rectangle.

ds 的积分就是安培矩形第一条边的长度。

In your illustration, the Amperian loop has 9 turns in it.

在您的插图中，Amperia 环路有 9 个匝。

Turn density equals number of turns inside the Amperian rectangle divided by the length of the Amperian rectangle.

匝密度等于安培矩形内的匝数除以安培矩形的长度。

It equals capital N, the number of turns of the wire inside the Amperian loop times the current in the wire.

它等于大写 N，即安培回路内导线的匝数乘以导线中的电流。

The closed loop integral of the whole Amperian rectangle equals the sum of the integrals for each of the sides of the rectangle.

整个安培矩形的闭环积分等于矩形每条边的积分之和。

So, side 2 is the right side of the Amperian rectangle, side 3 is the bottom side, and side 4 is the left side.

因此， 边 2 是安培矩形的右侧边，边 3 是底边， 边 4 是左侧。

So, the left-hand side of the equation is the magnitude of the magnetic field times the length of the side of the Amperian rectangle inside the solenoid.

因此，方程的左侧是磁场的大小乘以螺线管内部安培矩形的边长。

But, it does seem a little bit weird to still have variables in terms of the Amperian loop in the equation for the magnetic field inside a solenoid.

但是，在螺线管内部磁场的方程中仍然存在安培环方面的变量似乎有点奇怪。

And that means the magnetic field inside the solenoid equals the magnetic permeability of free space times the number of turns inside the Amperian loop times current in the wire all divided by the length of the Amperian loop.

这意味着螺线管内部的磁场等于自由空间的磁导率乘以安培环路内部的匝数乘以导线中的电流，然后再除以安培环路的长度。

Each time the wire goes around the cylinder is one " turn" of the solenoid, and for each " turn" of the solenoid, there is essentially one piece of the wire in the Amperian loop which has current in it.

电线每次绕圆柱体就是螺线管的一“圈”，并且对于螺线管的每一“圈”，安培回路中本质上有一根电线， 其中有电流。