本文针对天宫课堂第二课中的液桥实验进行理论研究. 基于液桥的对称性和体积不变性,根据最小势能原理,我们获得液桥形状的几何方程，据此探讨液桥形状随其长度的变化规律和最大长度. 发现一个描述液桥形状的特征参数R, 并揭示该参数与液桥内部压强的关系.

The theoretical research on liquid bridge experiment in the second lesson of heavenly palace classroom is conducted. Based on the symmetry and volume invariance of liquid bridge, the geometric equation of liquid bridge shape is obtained according to the principle of minimum potential energy, and the variation law of liquid bridge shape with its length and the maximum length are discussed. A characteristic parameter R describing the shape of the liquid bridge is found, and the relationship between the parameter and the internal pressure of the liquid bridge is revealed