问题 选择题

.已知磁敏电阻在没有磁场时电阻很小,有磁场时电阻变大,并且磁场越强阻值越大.为探测磁场的有无,利用磁敏电阻作为传感器设计了如图所示电路,电源的电动势E和内阻r不变,在没有磁场时调节变阻器R使电灯L正常发光,若探测装置从无磁场区进入强磁场区.则

A.电灯L变暗

B.电灯L变亮

C.电流表的示数增大

D.电流表的示数减小

答案

BD

进入磁场区后,磁敏电阻阻值增大,由于电源电动势E和内阻r不变,则路端电压增大,从而灯L两端的电压增大,电灯L变亮,B正确;但同时由于电路的总电阻增大,故电路中总电流减小,电流表示数减小,D正确。

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单项选择题

One thing that Ismael Matos, 23, says he’s learned on his job as a special agent with the Geek Squad, is that there are no stupid questions—not even when a customer asks where the power button is. The goal, Matos says, is first to "strip out the jargon. " You know what he means: those terms like gigs, Ram, and motherboard that civilians don’t typically use in everyday conversations. Once he establishes a common language with the customer, Matos can focus on building a relationshipone that he hopes will pay off in the future. Matos knows that clients often don’t have the same skills he does. His customers ask for help not only with setting up new computers and installing software, but also with digital cameras, wireless Internet access and even getting their iPod synced with iTunes.

We live in the age of Web2.0, when Internet viewers are fast becoming content creators. We may log in to social networking sites such as Digg and Technorati, rate or even upload videos on YouTube, and contribute and edit information on collaborate websites known as wikis.

But members of this expanding plugged-in population aren’t necessarily up to speed with the language of the web—or understand the technical lingo of the sales or customer service people they’re turning to for assistance. According to a "Cyber Stress" survey of 1,001 American broadband Internet service users, 46 percent said the typical tech support person uses an excess of technical language, and 61 percent said they would prefer a "computer therapist" who is compassionate and easy to talk to.

A question that online public relations strategist Sally Falkow says she’s hearing often these days is, "How do we cope with all this" she tells people, "There’s no way you can escape this. There’s a big conversation going on," and it’s important to learn how to be part of it.

If you’re at the earliest stage of the learning curve, start by reading technology-oriented columns and articles in magazines, newspapers and websites that are written for a general audience. Move up to more tech-oriented e-letters as you build a foundation. As you come across new tells, look them up online. Definitions at Wikipedia, the online encyclopedia written and edited by web users, may be helpful. You should also start associating with people who can help explain things. Look for groups that sponsor seminars or find a supportive online community. Don’t be afraid to guide your helper. Explain what you need to know, ask him or her to slow down and speak in basic terms.

It can be inferred that the Geek Squad is()

A. an IT training school

B. a computer support service

C. an iPod sales agency

D. a public relations institution