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1、1 新编大学英语四级考试模拟试卷(一)Part Writing(30 minutes)Directions:For this part,you are allowed 30 minutes to write a short essay entitled University Students Should Be Encouraged to Pay Their Tuition.You should write at least 120 words following the outline given below：1.大学生的学费大多由家长支付2.有人认为应该鼓励大学生自付学费3.你的观点注意：
2、此部分试题在答题卡1上。Part II Reading Comprehension(Skimming and Scanning)(15 minutes)Directions:In this part,you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet 1.For questions 1-7,mark Y(for YES)if the statement agrees with the information given in the passage;N(
3、for NO)if the statement contradicts the information given in the passage;NG(for NOT GIVEN)if the information is not given in the passage.For questions 8-10,complete the sentences with the information given in the passage.Wireless Power Scientists have tried to develop methods of wireless power trans
4、mission that could cut the clutter or lead to clean sources of electricity.While the idea may sound futuristic,it isnt particularly new.Nicola Tesla proposed theories of wireless power transmission in the late 1800s and early 1900s.One of his more spectacular displays involved remotely powering ligh
5、ts in the ground at his Colorado Springs experiment station.Teslas work was impressive,but it didnt immediately lead to widespread,practical methods for wireless power transmission.Since then,researchers have developed several techniques for moving electricity over long distances without wires.Some
6、exist only as theories or prototypes,but others are already in use.If you have an electric toothbrush,for example,you probably take advantage of one method every day.A toothbrushs daily exposure to water makes a traditional plug-in charger potentially dangerous.Ordinary electrical connections could
7、also allow water to seep into the toothbrush,damaging its components.Because of this,most toothbrushes recharge through inductive coupling.Inductive coupling uses magnetic fields that are a natural part of currents movement through wire.Any time electrical current moves through a wire,it creates a c
8、ircular magnetic field around the wire.Bending the wire into a coil amplifies the magnetic field.The more loops the coil makes,the bigger the field will be.If you place a second coil of wire in the magnetic field youve created,the field can induce a current in the wire.This is essentially how a tran
9、sformer works,and its how an electric toothbrush recharges.It takes three basic steps:1.Current from the wall outlet flows through a coil inside the charger,creating a magnetic field.In a transformer,this coil is called the primary winding.2.When you place your toothbrush in the charger,the magnetic
10、 field induces a current in another coil,or secondary winding,which connects to the battery.名师资料总结-精品资料欢迎下载-名师精心整理-第 1 页，共 17 页 -2 3.This current recharges the battery.You can use the same principle to recharge several devices at once.For example,the Splashpower recharging mat and Edison Electrics P
11、owerdesk both use coils to create a magnetic field.Electronic devices use corresponding built-in or plug-in receivers to recharge while resting on the mat.These receivers contain compatible coils and the circuitry necessary to deliver electricity to devices batteries.A newer theory uses a similar se
12、tup to transmit electricity over longer distances.Well look at how it works in the next section.Resonance and Wireless Power Household devices produce relatively small magnetic fields.For this reason,chargers hold devices at the distance necessary to induce a current,which can only happen if the coi
13、ls are close together.A larger,stronger field could induce current from farther away,but the process would be extremely inefficient.Since a magnetic field spreads in all directions,making a larger one would waste a lot of energy.In November 2006,however,researchers at MIT reported that they had disc
14、overed an efficient way to transfer power between coils separated by a few meters.The team,led by Marin Soljacic,theorized that they could extend the distance between the coils by adding resonance to the equation.Research at MIT indicates that induction can take place a little differently if the ele
15、ctromagnetic fields around the coils resonate at the same frequency.The theory uses a curved coil of wire as an inductor.A capacitance plate,which can hold a charge,attaches to each end of the coil.As electricity travels through this coil,the coil begins to resonate.Its resonant frequency is a produ
16、ct of the inductance of the coil and the capacitance of the plates.As with an electric toothbrush,this system relies on two coils.Electricity,traveling along an electromagnetic wave,can tunnel from one coil to the other as long as they both have the same resonant frequency.The effect is similar to the way one vibrating trumpet can cause another to vibrate.As long as both coils are out of range of one another,nothing will happen,since the fields around the coils arent strong enough to affect much
