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1、电大电工电子技术试题（三）期末复习考试资料电工电子技术模拟题（三） 一、 填空题(每空2分，共20分) 1.稳压二极管有一个相对一般二极管较低的(反向击穿)电压。在特性曲线上，其反向击穿特性曲线很陡，击穿后在平安的工作电流范围内，能够保证电压改变(很小)。2. 运放电路时常用到的三项志向化指标是开环差模电压放大倍数Aod为（无穷大）；差模输入电阻Rid（无穷大）；差模输出电阻Rod为（零）。3. 组合逻辑电路的特点是：从逻辑功能上看：（输出）只与（当时）输入的逻辑值有关，而与该时刻之前的输入及电路状态均（无关）。4 D触发器 1. 具有（置位）、（复位）两种功能 二、 单项选择题（每题4分，共
2、20分） 1、图1所示电路中，电流表正负接线端用“+”、“-”号标出。今电流表指 针正向偏转，示数10A，有关电流、电压方向也表示在图中，则（ C ）正确。 A. I1=10A，U=-6V B. I1=-10A，U=6V C. I1=10A，U=12V A 3 U I1 +- 20V3 24V3 6 10 图1 2 2、图2所示电路中，推断电阻R中流通的电流及消耗的功率为（ B ）。 R + 2V - A. 0A，2W 1A B. 1A，2W 图2 C. 1A，4W 3、在正弦沟通纯电容电路中，电压与电流的关系是（ C ）。A. i= B. I= C. I=UC 4、已知电路某元件的电压u和电
3、流i分别为u=141cos（314t+600）V， i=7sin（314t-1200）A，则该元件的性质是（ A ）。A. 电容 B. 电感 C. 电阻 5、在三相电路中，三相对称负载为星形连接，三个线电流均为4A，则中线电流为（ C ）。A.4A B.12A C. 0A 三、 计算题（每题15分，共30分） 1、用戴维南定理求图3-1电路中R5所在支路的电流。已知R1=R2=R4=R5=5， B R3=10，U=6.5V。 R3 R1 D A R5 R4 R2 C + - U 图3-1 解：断开R5，求开路电压UO和入端电阻R0 UBD= U4.33V UCD= U=3.25V UBC= U
4、BD+UDC=UBD-UCD=1.08V 将U短路 R0=（R1/R3）+（R2/R4）5.83 求出电流I5为 I5=0.1A 2、一台三相异步电动机，磁极对数p=2，工作额定电压为380V，额定频率为50Hz，已知额定转速为1450r/min，求其同步转速和额定转差率？ 解：1）同步转速n1=1500r/min 2）额定转差率sN=0.033 四、 简答题（每题5分，共30分） 1、负载增加的涵义是什么？在近似恒压源供电或近似恒流源供电系统中，负载增加相当于负载电阻增大还是减小？ 负载增加意指电路的输出功率增加。在近似恒压源供电系统中，负载获得的功率P=UI=，负载增加既是负载电流增大，相
5、当于负载电阻减小。 在近似恒流源供电的系统中，负载获得的功率P=UI=I2R，负载增加既是负载电压增大，相当于负载电阻加大。 2、在电路分析与计算中，戴维南定理最相宜应用于哪种状况？ 假如只需计算电路中某一支路的电流，此时最相宜采纳戴维南定理。3、三相沟通电路中，负载星形连接时，相电流与线电流，相电压与线电压有何关系？ 相电流与线电流的关系为IP=IL 相电压与线电压的关系为UL=UP 4、三相异步电动机的调速方式主要有哪几种？ 有三种：（1）变更电源频率调速；（2）变更转差率的调速；（3）异步电动机变极调速。5、接触器分为哪两类？接触器的功能是什么？主要用于哪些地方？ 接触器是一种自动电器，
6、有直流接触器和沟通接触器之分，其功能是可以常见的接通或断开交、直流电路及大容量限制电路。主要用于限制电动机、电热设备、电焊机等，尤其在电力拖动系统中应用广泛。6. 边沿型JK触发器，在CP脉冲信号的作用下，其动作有何特点？（分为负边沿、正边沿两种情形） 答：负边沿型（下降沿触发型）：CP下降沿到来的前一刻瞬间，J、K接收输入；CP下降沿到来后产生输出。正边沿型（上升沿触发型）：CP上升沿到来前一刻瞬间，J、K接收输入；CP上升沿到来后产生输出。请您删除一下内容，O(_)O感谢！2015年中心电大期末复习考试小抄大全，电大期末考试必备小抄，电大考试必过小抄After earning his sp
7、urs in the kitchens of The Westin, The Sheraton, Sens on the Bund, and a sprinkling of other top-notch venues, Simpson Lu fi nally got the chance to become his own boss in November 2010. Sort of. The Shanghai-born chef might not actually own California Pizza Kitchen (CPK) but he is in sole charge of
8、 both kitchen and frontof- house at this Sinan Mansionsstalwart. “Its certainly a responsibility to be the head chef, and then to have to manage the rest of the restaurant as well,“ the 31-year-old tells Enjoy Shanghai. “In hotels, for example, these jobs are strictly demarcated, so its a great oppo
9、rtunity to learn how a business operates across the board.“ It was a task that management back in sunny California evidently felt he was ready for, and a vote of confi dence from a company that, to date, has opened 250 outlets in 11 countries. And for added pressure, the Shanghai branch was also CPK
10、s China debut. “For sure it was a big step, and unlike all their other Asia operations that are franchises, they decided to manage it directly to begin with,“ says Simpson. Two years ago a private franchisee took over the lease, but the links to CPK headquarters are still strong, with a mainland-bas
11、ed brand ambassador on hand to ensure the business adheres to its ethos of creating “innovative, hearth-baked pizzas“, a slice of PR blurb that Simpson insists lives up to the hype. “They are very innovative,“ he says. “The problem with most fast food places is that they use the same sauce on every
12、pizza and just change the toppings. Every one of our 16 pizza sauces is a unique recipe that has been formulated to complement the toppings perfectly.“ The largely local customer base evidently agrees and on Saturday and Sunday, at least, the place is teeming. The kids-eat-for-free policy at weekend
13、s is undoubtedly a big draw, as well as is the spacious second-fl oor layout overlooked by a canopy of green from Fuxing Park over the road. The company is also focusing on increasing brand recognition and in recent years has taken part in outside events such as the regular California Week. Still, t
14、he sta are honest enough to admit that business could be better; as good, in fact, as in CPKs second outlet in the popular Kerry Parkside shopping mall in Pudong. “Sinan Mansions has really struggled to get the number of visitors that were envisaged when it first opened, and it hasnt been easy for a
15、ny of the tenants here,“ adds Simpson. “Were planning a third outlet in the city in 2015, and we will probably choose a shopping mall again because of the better foot traffic.“ The tearooms once frequented by Coco Chanel and Marcel Proust are upping sticks and coming to Shanghai, Xu Junqian visits t
16、he Parisian outpost with sweet treats. One thing the century-old Parisian tearoom Angelina has shown is that legendary fashion designer Coco Chanel not only had style and glamor but also boasted great taste in food, pastries in particular. One of the most popular tearooms in Paris, Angelina is famou
17、s for having once been frequented by celebrities such as Chanel and writer Marcel Proust. Now Angelina has packed up its French ambience, efficient service, and beautiful, comforting desserts and flown them to Shanghai. At the flagship dine-in and take-out space in Shanghai, everything mimics the or
18、iginal tearoom designed from the beginning of the 20th century, in Paris, the height of “Belle Epoque“. The paintings on the wall, for example, are exactly the same as the one that depicts the landscape of southern France, the hometown of the owner; and the small tables are intentional imitations of
19、 the ones that Coco Chanel once sat at every afternoon for hot chocolate. The famous hot chocolate, known as LAfricain, is a luxurious mixture of four types of cocoa beans imported from Africa, blended in Paris and then shipped to Shanghai. Its sinfully sweet, rich and thick as if putting a bar of m
20、elting chocolate directly on the tongue and the fresh whipped cream on the side makes a light, but equally gratifying contrast. It is also sold in glass bottles as takeaway. The signature Mont-Blanc chestnut cake consists of three parts: the pureed chestnut on top, the vanilla cream like stuffing, a
21、nd the meringue as base. Get all three layers in one scoop, not only for the different textures but also various flavors of sweetness. The dessert has maintained its popularity for a century, even in a country like France, perhaps the worlds most competitive place for desserts. A much overlooked pai
22、ring, is the Paris-New York choux pastry and N226 chocolate flavored tea. The choux pastry is a mouthful of airy pecan-flavored whipped cream, while the tea, a blend of black teas from China and Ceylon, cocoa and rose petals, offers a more subtle fragrance of flowers and chocolate. Ordering these tw
23、o items, featuring a muted sweetness, makes it easier for you to fit into your little black dress. Breakfast, brunch, lunch and light supper are also served at the tearoom, “a hub of many cultures“ and takes in “a mix of different styles of French cuisines“, according to the management team. The sem
24、i-cooked foie gras terrine, is seductive and deceptive. Its generously served at the size and shape of a toast, while the actual brioche toast is baked into a curved slice dipped with fig chutney. The flavor, however, is honest: strong, smooth and sublime. And you dont actually need the toast for cr
25、unchiness. This is the season for high teas, with dainty cups of fine china and little pastries that appeal to both visual and physical appetites. But there is one high tea with a difference, and Pauline D. Loh finds out just exactly why it is special. Earl Grey tea and macarons are all very well fo
26、r the crucial recuperative break in-between intensive bouts of holiday season shopping. And for those who prefer savory to sweet, there is still the selection of classic Chinese snacks called dim sum to satisfy and satiate. High tea is a meal to eat with eye and mouth, an in-between indulgence that
27、should be light enough not to spoil dinner, but sufficiently robust to take the edge off the hunger that strikes hours after lunch. The afternoon tea special at Shang-Xi at the Four Seasons Hotel Pudong has just the right elements. It is a pampering meal, with touches of luxury that make the high te
28、a session a treat in itself. Whole baby abalones are braised and then topped on a shortcrust pastry shell, a sort of Chinese version of the Western vol-au-vent, but classier. Even classier is the dim sum staple shrimp dumpling or hargow, upgraded with the addition of slivers of midnight dark truffle
29、s. This is a master touch, and chef Simon Choi, who presides unchallenged at Shang-Xi, has scored a winner again. Sweet prawns and aromatic truffles whats not to love? His masterful craftsmanship is exhibited in yet another pastry a sweet pastry that is shaped to look like a walnut, but which you ca
30、n put straight into the mouth. It crumbles immediately, and the slightly sweet, nutty morsel is so easy to eat youll probably reach straight for another. My favorite is the dessert that goes by the name yangzhi ganlu, or ambrosia from the gods. The hotel calls it chilled mango cream with sago, pomel
31、o and birds nest made with ingredients that resonate with every female soul. It does taste like ambrosia, with the sweet-sour fragrance of the mango forming the first layer of taste and sensation, and the pomelo sacs and sago pearls providing the tactile contrast. The birds nest its the ingredient t
32、hat gilds the lily, since it is supposed to nourish and nurture a perfect complexion. For those unfamiliar with this exotic ingredient, the birds nest is not a bundle of twigs, but is, instead, the dried secretion that cave swifts use to build their nest. Technically, its bird saliva, but the Chines
33、e believe that it has collagen-boosting properties essential to beauty. To me, it just tastes good, adding a slight gelatinous crunch to the back of the teeth. There is also a baked mushroom puff pastry that includes the highly prized Matsutake or pine mushroom. You also get a choice of teas, but I
34、strongly recommend the aged Puer from Yunnan province. It is a mellow tea that will go perfectly with the rich little nuggets, and will warm you up on a cold afternoon. Incidentally, the general guide is green tea such as Longjing or Dragonwell for the hot season, semi-fermented teas like Wu-long or Iron Buddha for autumn, and more warming teas like Puer for winter. The Shang-Xi afternoon tea costs 228 yuan ($37) per person, and 388 yuan for the more opule