用“电势”分析恒定电流是常用的方法.应用时,先把闭合电路看成一个环形电场,电场线从电源正极出发沿闭合电路回到电源负极,电流顺着电场线从高电势流向低电势,每经过一个用电器,就有一定的电势降低,电势差就是用电器两端的电压. It is a common method to analyze the constant current with “potential”. In application, first consider the closed circuit as an annular electric field. The electric field line starts from the positive pole of the power supply and returns to the negative pole of the power supply along the closed circuit. The current flows from the high potential to the low potential along the electric field line. Every time an appliance is used, there is a certain potential drop. The potential difference is the voltage across the appliance.