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在交流电路的分析计算中，也采用假定电流参考方向的方法，用正负值来表示瞬时实际电流的流向。
In the analysis and calculation of AC circuit, the current reference direction is assumed, and the positive and negative values are used to represent the flow direction of instantaneous actual current.
电工学网在电工与电子基础学习环节的电路图中如未加说明，图中所标电流方向均为参考方向。电路中在没有设定参考方向的情况下，电流的正和负是没有意义的。
If not specified in the circuit diagram of basic electrical and electronic learning link of electrical engineering network, the marked current direction in the diagram is the reference direction. When there is no reference direction set in the circuit, the positive and negative currents are meaningless.
电动势、电位和电压
Electromotive force, potential and voltage
电动势反映电源中电源力做功的能力，在数值上等于电源力把单位正电荷从电源的负极搬到正极所做的功。如果是直流电源，电动势是恒定的，用大写字母E表示；如果是交流电源，电动势是变化的，用小写字母e表示。 单位为伏特（V）。金南春晨YCB扁电缆 卷筒扁电缆 行车扁电缆
Electromotive force reflects the power supply's ability to do work, which is equal to the power supply force's work to move the unit positive charge from the negative pole to the positive pole. In case of DC power supply, the electromotive force is constant, which is indicated by the capital letter E; in case of AC power supply, the electromotive force is variable, which is indicated by the small letter E. The unit is volts (V).
直流电源的极性表示电动势的方向是由电源负极指向电源正极，用符号-和+表示，如上图（直流电动势的表示方法）所示。在交流电源内，如电动势的实际方向不知道时，也可假定电动势的参考方向。
The polarity of the DC power supply indicates that the direction of the EMF is from the negative pole of the power supply to the positive pole of the power supply, which is indicated by the symbol - and + as shown in the figure above (expression method of the DC EMF). In AC power supply, if the actual direction of electromotive force is not known, the reference direction of electromotive force can also be assumed.
电位：电场中某点的单位正电荷具有的电位能，称为该点的电位，用符号V表示，单位为伏特（V）。
Potential: the potential energy possessed by the unit positive charge at a certain point in the electric field, which is called the potential at that point, expressed by the symbol V, and the unit is volt (V).
