electromagnetic constant

例句：

1. 1. The speed of light is afundamental constant in electromagnetism.
   光速是电磁学中的一个基本常数。
2. 2.The magnetic field strength is directly proportional tothe distance from the Earth's surface.
   磁场强度与地球表面的距离成正比。
3. 3. Theelectric charge of an electron is directly relatedto its mass and velocity.
   电子的电荷与其质量和速度直接相关。