【正文】 Section 6 Exercise 3。阻抗不是一個相量，因此不能通過把它乘以并取其實部把它轉換成時域形式。疊加法原理表明線性電路某個元件兩端的電壓（或流過元件的電流）等于每個獨立源單獨作用時該元件兩端的電壓（或流過元件的電流）的代數(shù)和。另一種方法是求出每個獨立源對變量的作用然后把它們進行疊加。而對于任何非線性電阻器我們應當始終這么稱呼它，非線性電阻器不應當必然地被視為不需要的元件。我們通常應當把線性電阻器僅僅稱為電阻器。（同位語從句）Section 2 Exercise 3Section 3 Exercise3 必須強調(diào)的是線性電阻器是一個理想的電路元件；它是物理元件的數(shù)學模型。（賓語從句）Electrons always move toward where the potential is 。（定語從句）Now we can determine where the slope is 。（定語從句）The places where small puters can be used appear 。（表語從句）The places where small puters can be used appear 。（表語從句）You should determine which of the following functions is 。（狀語從句）Before one studies a system, it is necessary to define and discuss some important ，必須定義并討論一些重要的術語。（動名詞作介賓）Mechanization is using machines instead of hand 。（現(xiàn)在分詞短語作狀語）Doing experiment is of great help to 。 stations are usually located near a river or lake because large quantities of cooling water are needed to condense the steam as it exhausts from the ，這是因為需要大量的冷卻水在蒸汽從汽輪機排出時將其冷凝。 instance, in the United States, water power accounts for less than 20% of the total and that percentage will drop because most of the available sources of water power have been ，在美國，水電在全部電力中所占的比例不到20%，并且，因為大多數(shù)可用的水電資源已被開發(fā)，該百分數(shù)還會下降。 synchronous machine as an AC generator driven by aturbine is the device which converts mechanical energy to electrical energy, in powers ranging up to ，同步電機是將機械能轉化為電能的設備，其功率范圍高達1500MW。 loads absorb electric energy from the power system and converts it into energy of other forms, which may be heat energy to heat water or to melt irons, or mechanical energy to drive a machine, ，并將其轉換為其他形式的能量，可能是燒水或溶化鋼鐵的熱能，或者是驅動機器的機械能等。 illustrated in , the aggregated load represented at a transmission substation(bus A)usually includes, in addition to the connected load devices, the effects of substation stepdown transformers…，在輸電變電站（母線A）所給出的集合負荷，除了所連接的負荷設備以外，通常還包括變電站降壓變壓器的影響……。 industrial customers are supplied by primary feeders at this voltage level from the primary system, which also supplies the distribution transformers providing secondary voltages over singlephase threewire circuits for residential and mercial customers at 120 V/240 。這樣的裝置稱之為電容器，其儲存電能的能力稱為電容。 of the three phases can be restored by exchanging the positions of the conductors at regular intervals along the line so that each conductor occupies the original position of every other conductor over an equal distance, as shown in ，沿線路方向每隔一定間隔就交換導線位置，使每根導線都能占據(jù)具有相同輸電距離的其他各導線的初始位置，以重建三相平衡?；颍弘娙荽嬖谟趯w之間，等于導體之間單位電壓對應的電量。 definite capability can be specified for a line of a given voltage, however, because capability is dependent on the thermal limits of the conductor, allowable voltage drop, reliability, and requirements for maintaining synchronism between the machines of the system, which is known as ，無法為給定電壓等級的線路指定確切的容量，這是因為容量取決于導線的發(fā)熱極限、允許的電壓降落、可靠性和維持系統(tǒng)中的發(fā)電機同步的要求（這被認為是穩(wěn)定性）。 the system expands and higher