An electric current acts in that very way,that is to say,it takes time to start,and once started,it

high enough.

To his surprise, the electric current flows through a conductor ____________(就好像液体一样).

ility of an electric current to heat a fire.

A．devices

B．appliances

C．apparatus

D．instruments

___.

A．the current in one place is not strong enough to give a shock

B．the fish' s electric cells are filled with jelly-like substance

C．to complete the circuit, you have to touch the fish in two places

D．a torpedo' s electric cells contain more than one electric plates

_________．

A.a torped0’s electric cells contain more than one electricDlates

B.to complete the circuit，you have to touch the fish in twoDlaces

C.the current in one place is not strong enough to give a shock

D.the fish’s electric cells are filled with jelly-like substance

have been used at a rapidly increasing rate. The supply of these【C1】______is limited and electric power is very【C2】______in many places. Some scientists believe solar energy is the only【C3】______that can meet the world's enormous【C4】______for power. Great progress had been made harnessing the sun. Not only is the sun now used in cooking, 【C5】______it also supplies power for【C6】______things as beacon lights for ships and airplanes. It【C7】______telephone lines, portable radios, electric clocks, hearing aids, and even communication satellites. Some homes and office buildings in U. S. A. are now being【C8】______with solar energy. The three most【C9】______types of solar equipment so far are the furnace, the still(蒸馏器)and the cell. Solar furnaces heat water or air,【C10】______is then circulated through a building to make it comfortable. Solar stills are【C11】______important because they can provide【C12】______water at a relative cheap rate. Salt can easily be【C13】______from sea water with solar still. The most highly developed type of solar【C14】______equipment is the solar cell. Some cells are so【C15】______that they can turn 16% of the energy they receive from the sun【C16】______electric energy. One of the cell's biggest advantages is【C17】______it can be made either small enough to carry【C18】______large enough to produce current that can run an automobile. Besides, it has a very long life. It is still too expensive for the【C19】______consumer but when ways are【C20】______to produce it more cheaply, we can expect its use to be widely-spread.

【C1】

A．materials

B．metals

C．reserves

D．fuels

m predicted superconductivity. This phenomenon was discovered in 1911 by Onnes while he was studying frozen mercury.

More than 40 years passed before physicists were able to offer an explanation for superconductivity. The accepted theory, developed in the 1950s, holds that the fundamental behavior. of electrons changes at very low temperatures because of the effects of quantum mechanics. Electrons are tiny particles that make up the outer part of an atom, circling rapidly around the nucleus of the atom. In a regular conductor—a metal that conducts an electric current—the outermost electrons are not bound tightly to the atoms, and so they move around relatively freely. The flow of these electrons is an electric current.

At normal temperatures, a conductor's electrons cannot move completely freely through the metal because they are "bumped around" by the metal's atoms. But according to the leading theory of superconductivity, when a metal is very cold, electrons form. pairs. Then, like couples maneuvering on a crowded dance floor but never colliding, the paired electrons are able to move unimpeded through the metal. In pairing up, it seems, the electrons are able to "blend together" and move in unison without resistance. This explanation seems to account for superconductivity at extremely low temperatures, but in 1986 scientists in Switzerland found that some metal-containing ceramics are superconductors at much higher temperatures. By 1992, scientists had developed ceramics that become superconducting at - 297'F, and some researchers speculated that room-temperature superconductors may be possible. Scientists are still trying to formulate a theory for high-temperature superconductivity.

The new ceramic materials can be maintained at their superconducting temperatures, with relatively inexpensive liquid nitrogen rather than the much colder and much more costly liquid helium required by metal superconductors. The cost difference could make superconductivity practical for many new technologies. For example, magnetically levitated trains, which require superconducting electromagnets, would be much cheaper to build than they are now. Superconducting devices might also be used for advanced power transmission lines and in new types of compact, ultrafast computers. But for the time being, superconductivity is finding application mostly in scientific research and in some kinds of medical imaging devices.

The flow of an electric current in a regular conductor is made possible by the fact that______.

A．electrons circle rapidly around the atom

B．the outermost electron move relatively freely around the atom

C．the innermost electrons stick to the atom

D．the outermost electrons are bound tightly to the inner ones

onsumers to discard last year' s car or clothing in【C2】______of the current models with the latest designs. Some people are【C3】______that they must"【C4】______the Jones," that they must have whatever their neighbors have. The old car or the old stereo set【C5】______work perfectly, but a newer and bigger one might【C6】______the family' s esteem in the community. Possessions become【C7】______of financial success; they elevate【C8】______social status.

Advertisers also【C9】______to the American desire to look youthful and be physically attractive. Commercials attempt to sell many products—shampoo, toothpaste, deodorant and soap, for example—【C10】______implying that their particular【C11】______will help its user be more appealing.

But Americans also make many【C12】______for practical reasons. They buy【C13】______devices to do routine household chores more quickly and easily. Every housewife wants a vacuum cleaner, an electric mixer, a steam iron, an automatic clothes washer and dryer, and a dishwasher.【C14】______every home-owning husband would like a power lawn mower, as now -blower, and an electric drill.

Americans also buy things【C15】______they like to do things. Equipment【C16】______hobbies and books about "do-it-yourself' projects are very popular. Americans want to know how to cook with a "continental" flair while refinishing the bedroom furniture and【C17】______a million dollars in the stock market. The American【C18】______of activity is part of a generally【C19】______outlook on life, a belief that the value of knowledge is【C20】______to its usefulness.

【C1】

A．what

B．it

C．that

D．which

从供选择的答案中选出应填入下面一段英文中______内的正确答案。

A light-emitting diode (LED) is a semiconductor(1)that emits visible light when an electric current passes throughit.The light is not particularly(2), but in most LEDs it is monochromatic, occurring at a single(3). The output from an LED can range from red (at a wavelength of approximately 700 nanometers) to blue-violet (about 400 nanometers). Some LEDs(4)infrared (IR) energy (830 nanometers or longer); such a device is known as an infrared-emitting diode (IRED).

An LED or IRED(5)of two elements of processed material called P-type semiconductors and N-type semiconductors. These two elements are(6)in direct contact, forming a region called the P-N junction. In this respect, the LED or IRED(7)most other diode types, but there are important(8). The LED or IRED has a transparent package, allowing(9)or IR energy to pass through. Also, the LED or IRED has a large PN-junction area whose(10)is tailored to the application.

供选择的答案：

1．wavelength 2．shape 3．emit 4．device 5．resembles

6．bright 7．visible 8．consists 9．differences 10．placed

？Read the article below about corporate culture on the opposite page.

？For each question 13-18, mark one letter (A, B, C or D) on your Answer Sheet for the answer you choose.

The term corporate culture refers to an organization's value system. Managerial philosophies, workplace practices, and organizational network are included in the concept of corporate culture. Tyson Food's corporate culture is reflected in the fact that everyone—even CEO Don Tyson wears clothes of a yellowish brown color on the job.

The leaders who developed the company and the corporate culture typically shape the corporate culture.One generation of employees passes on a corporate culture to newer employees. Sometimes this is part of formal training. New managers who attend McDonald's Hamburger University may learn skills in management,but they also pick up the basics of the organization's corporate culture. Employees can absorb corporate culture through informal contacts as well, by talking with other workers and through their experiences on the job.

Corporate culture has a major impact on the success of an organization. In organizations with strong cultures,everyone knows and supports the organizations' objectives. In those with weak cultures, no clear sense of purpose exists. In fact, the authors of the classic book In Search of Excellence concluded the presence of a strong corporate culture was the single common thread among many diverse but highly successful companies such as General Electric and McDonald's.

As you can imagine, changing a company's corporate culture can be very difficult. But some managers try to do just that when they feel the current culture is weak, or when the organization's objectives change and the old culture no longer fits. Sometimes the competitive situation of a company changes.For instance, electric utilities, which once had their profits guaranteed by public regulation, now face more competition than ever. Firms that were comfortable competing against other American companies now find themselves fighting competitors from overseas, too.

Management expert Peter Duckers feels that, rather than trying to change culture, managers should focus on changing employees and corporate practices, as follows.

？Define what results are needed. Specify in measurable terms what the organization or department,or office) needs to achieve.

？Determine where these results are already being achieved within the current organization. Analyze the departments that are already effective and find out what they are doing differently from the rest.

？Determine what top management can do to encourage these good results. Duckers suggests that executives openly ask what they can do to help, and then do it.

？Change the reward system—or develop a new one—to recognize these effective practices. When employees realize that the organization really does reward the new approach, they will adopt it much more quickly. Whether one wants to change an organization culture or not, it is important to choose managers and employees whose personal styles fit the organization's goals.

According to the passage, corporate culture

A．means the cultural atmosphere in a company.

B．is established by top leaders and can't be changed.

C．involves the core values of a company.

D．has little influence on the performance of a company.