英语翻译专英There may be times,however,when the model is inadequat

英语翻译
专英
There may be times,however,when the model is inadequate.The battery voltage,for example,may drop as more and more current is drawn,or as the battery ages.The lightbulb’s resistance may change as it heats up,and the filament may have a bit of inductance and capacitance associated with it as well as resistance so that when the switch is closed,the current may not jump instantaneously from zero to some final,steadystate value.The wires may be undersized,and some of the power delivered by the battery may be lost in the wires before it reaches the load.These subtle effects may or may not be important,depending on what we are trying to find out and how accurately we must be able to predict the performance of the circuit.If we decide they are important,we can always change the model as necessary and then proceed with the analysis.
The first property,known as Kirchhoff’s current law (abbreviated KCI),states that at every instant of time the sum of the currents flowing into any node of a circuit must equal the sum of the currents leaving the node,where a node is any spot where two or more wires are joined.This is a very simple,but powerful concept.It is intuitively obvious once you assert that current is the flow of charge,and that charge is conservative-neither being created nor destroyed as it enters a node.Unless charge somehow builds up at a node,which it does not,then the rate at which charge enters a node must equal the rate at which charge leaves the node.

也许有些时候,然而,当模型是不能够充分说明的.电池电压,例如,可能会下降,随着电流的逐渐增加,电压会降低,或随着电池的老化电压也降低.当灯泡被加热时,电阻会增加,并且灯丝可能有电感和电容与它相关的阻力,这样,当开关关闭时,电流可能不会瞬间从零跳到最终的稳态值.可能是电线不够粗,以及由电池传递的能量在到达负荷前损失在线路里.这些微妙的影响可能并不重要,这取决于我们试图求出什么和我们必须能够预测的电路的精确性的范围.如果我们决定他们是重要的,我们可以根据需要随时更改模型,然后进行分析.
第一个属性,熟知的基尔霍夫电流定律（简称KCL）,指出在每一个瞬间的到任何一个电路节点电流之和必须等于该离开节点的电流,该接点可以是任何一个由两条及以上的电线的连接点.这是一个非常简单,但是非常有力的概念.显而易见的,当你认为电流是电荷的移动,电荷进入到一个接点时电荷不被创造和不消失,除非以某种方式积聚电荷在一个节点,它没有,电荷进入节点的速度一定等于电荷离开节点的速度.
原著：YXJ