主要区别-电动势与电位差

电动势和电位差这两个术语都描述了电路中涉及电子的能量转移。电动势和电位差之间的主要区别在于，电动势是指库仑电荷在电路中所获得的电能，而电位差则是指库仑电荷所损失的电能。

什么是电动势(emf)？

EMF ( ) stands for electromotive force. In a cell or a generator, the EMF refers to the amount of electrical energy given to each coulomb of electr***. This electrical energy has been created by conversion of another form of energy into electrical energy (e.g. chemical energy to electrical energy in a cell, or mechanical energy to electrical energy in a generator).

注意，即使包含了force一词，EMF也与force无关。相反，这个术语与电子的电能的获得和损失有关。

什么是电位差(potential difference)？

In an electrical circuit, the potential difference  between any two points in the circuit is the energy lost by a coulomb of charge as it travels between those two points. Potential difference can be measured using a voltmeter, and it is expressed in units of volts.

所以，电动势这个词用来描述电子获得电能的例子，而电位差用来描述电子失去电能的例子。在电路中的一个闭合环周围，能量必须守恒，因此这就产生了基尔霍夫第二定律，即闭合环周围的电磁场之和等于该环周围的电位差之和。

如果一个细胞是理想的，那么它给通过它的电子提供电能，这些电子从细胞中出来，而不会失去它们所获得的任何电能。然而，实际上，电子甚至在离开细胞之前就失去了获得的一些能量。我们说能量是由于细胞的内阻而损失的。在电路分析中，可以想象这种内阻来自电池内部的电阻器：

An ideal cell (left) and a real cell (with internal resistance) (right)

The terminal potential difference across a cell refers to the energy gained by a coulomb of electr*** as they pass through it, minus the energy they lose due to internal resistance. If the EMF is  , the internal resistance is  , the current through the cell is  then the terminal potential difference  given by:

Within cells, electr*** gain energy, and then lose some of it.

电动势(emf)和电位差(potential difference)的区别

意思

电动势描述电路中电子的电能增益。

电位差描述了电子在电路中传播时的电能损失。

Image Courtesy

“Batteries Included” by Vincent Brown (Own work) [CC BY 2.0], via flickr