電工電子技術(shù)模擬題（一）

1、電工電子技術(shù)模擬題（一）一、 填空題(每空2分，共20分) 1 任意時(shí)刻，流入電路中任一（節(jié)點(diǎn)）的電流之和恒等于（流出）該節(jié)點(diǎn)的電流之和。2 放大電路的信號(hào)源內(nèi)電阻（RS）越高，電路的電壓放大倍數(shù)（越小）。3對(duì)于TTL門(mén)電路， 1. 輸出為（高電位）時(shí)，帶負(fù)載的能力弱。輸出為（低電位）時(shí)，帶負(fù)載的能力強(qiáng)。4.磁力線越密表示磁場(chǎng)（越強(qiáng)）。5描述邏輯功能的方法有： （真值表）、（邏輯圖）、（表達(dá)式）。二、 單項(xiàng)選擇題（每題4分，共20分） 1、圖1所示電路中U為（ A ）。2A - 45V + A. 30V U 15 B. -10V 圖1 C. -40V 2、圖2所示電路中，電源電壓不變，而頻率升

2、高，各燈泡的亮度變化是（ B ）。C B A u A. 燈泡A變亮 L C R B. 燈泡B變亮 圖2 C. 燈泡C變亮 3、圖3所示變壓器，已知原方N1=300匝， R=8，則從原方看入的電阻Ri是72，則變壓器副方繞組N2為（ C ）。A.200匝 B.300匝 C. 100匝 N2 N1 Ri 圖3 R 4、穩(wěn)壓二極管是利用其工作在（ C ）時(shí)電壓變化極小的特性，使兩端電壓得到穩(wěn)定的。A. 正向 B.反向 C. 反向擊穿 5、放大電路引入電壓并聯(lián)負(fù)反饋，可以使輸入電阻（ B ）。A. 增大 B.減小 C. 不變 三、 計(jì)算題（每題15分，共30分） 1圖3-1所示電路可用來(lái)測(cè)量電源的數(shù)值

3、及其內(nèi)阻，圖中標(biāo)出的U和R0組成某實(shí)際電壓源。已知R1=2.6，R2=5.5，當(dāng)開(kāi)關(guān)K1閉合，K2打開(kāi)時(shí)，電流表讀數(shù)為2A；打開(kāi)K1，閉合K2后，讀數(shù)為1A，試求U和R0。 R2 R1 R0 圖3-1 U K2 K1 解：K1閉合，K2打開(kāi)，有 I1（R0+R1）=U K1打開(kāi)，K2閉合，有 I2（R0+R2）=U 聯(lián)立上兩式，得出 U=5.8V， R0=0.3 2、有一電感線圈，當(dāng)接在電壓為40V的直流電源上時(shí)，測(cè)得線圈電流為4A。當(dāng)接于電壓為220V、頻率為50HZ的正弦交流電源時(shí)，測(cè)得電流為10A，求線圈電阻與電感。解：直流電源作用時(shí) XL=L=0，R=40/4=10 交流電源作用時(shí) Z

4、=22 XL=19.6 L=62.4mH 四、 簡(jiǎn)答題（每題5分，共30分） 1、恒壓源的性質(zhì)是什么？ 恒壓源的性質(zhì)為（1）它的輸出電壓始終是恒定的，不受輸出電流的影響；（2）通過(guò)它的電流不由它本身決定，由與之相連的負(fù)載電阻決定。2、簡(jiǎn)述RLC串聯(lián)電路產(chǎn)生串聯(lián)諧振的特點(diǎn)？ （1）電路的阻抗最小并呈電阻性。（2）電路中的電流最大。（3）XL=XC，串聯(lián)諧振可在電容和電感兩端產(chǎn)生高電壓。3、如果需要電動(dòng)機(jī)連續(xù)運(yùn)行，那么對(duì)于三相異步電動(dòng)機(jī)功率的選擇要注意什么？ 功率選擇應(yīng)該以產(chǎn)生機(jī)械所需要的實(shí)際功率為依據(jù)。選擇的過(guò)大，效率和功率因數(shù)會(huì)很低，不經(jīng)濟(jì)。選擇的過(guò)小，電動(dòng)機(jī)長(zhǎng)時(shí)間工作在外額定過(guò)載狀態(tài)下，不僅

5、不能保證正常工作，還可能造成電動(dòng)機(jī)損壞。4、基本放大電路的組成原則是什么？ 答： 1電路中既有直流通路，又有交流通路。2電路由線性元件和非線性器件組成。3三極管工作在放大狀態(tài)，保證信號(hào)失真不超過(guò)允許范圍。5、引入電壓串聯(lián)負(fù)反饋和電流并聯(lián)負(fù)反饋，對(duì)放大電路的輸入、輸出電阻分別有什么影響？ 答：引入電壓串聯(lián)負(fù)反饋，會(huì)使輸入電阻增大，輸出電阻減?。灰腚娏鞑⒙?lián)負(fù)反饋，會(huì)使輸入電阻減小，輸出電阻增大。請(qǐng)您刪除一下內(nèi)容，O(_)O謝謝！2015年中央電大期末復(fù)習(xí)考試小抄大全，電大期末考試必備小抄，電大考試必過(guò)小抄After earning his spurs in the kitchens of The

6、 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 both kitchen and frontof-

7、 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 opportunity to learn how a bus

8、iness 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 CPKs China debut. “For sure i

9、t 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-based brand ambassador on han

10、d 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 pizza and just change the

11、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 weekends is undoubtedly a big dra

12、w, 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, the sta are honest enough t

13、o 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 any of the tenants here,“ a

14、dds 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 the Parisian outpost with s

15、weet 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 famous for having once been fre

16、quented 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 original tearoom designed fr

17、om 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 the ones that Coco Chanel

18、 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 melting chocolate directly

19、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, and the meringue as base. G

20、et 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 pairing, is the Paris-New Yor

21、k 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 two items, featuring a muted

22、 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 semi-cooked foie gras terrine

23、, 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 crunchiness. This is the sea

24、son 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 for the crucial recuperative

25、 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 should be light enough not

26、 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 tea session a treat in itsel

27、f. 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 truffles. This is a master touch,

28、 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 can put straight into the mo

29、uth. 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, pomelo and birds nest made with

30、 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 that gilds the lily, since it is supposed to nourish and n