In some dining halls, students pay directly for what they eat, while in others, they pay a fixed charge per term to cover catering overheads, and are then charged solely for the food they eat.

而在别的餐厅里学生每学期交固定数额的餐饮，然再所吃的食物单独付。

As a test charge moves closer to one of the fixed charges, the forces on it will be larger, thus the greater number of lines in that area.

随着电荷向其中一个固定电荷移动， 身上的力量正在增加。以及行数。