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如图所示，水平面上有一对平行光滑金属导轨，导轨左端串有一电阻R，金属杆ab垂直平放在两导轨上，整个装置处于竖直向下的匀强磁场中，忽略导轨的电阻，但ab杆的质量和电阻都不能忽略．现给ab杆施以水平向右的恒力F，在ab杆从静止开始向右运动过程中，外力F做的功______（选填：“大于”、“等于”或“小于”）整个电路消耗的电功，磁场对ab杆作用力的功率______（选填：“大于”、“等于”或“小于”）电阻R上消耗的电功率．

答案

在ab杆从静止开始向右运动过程中，ab杆的动能逐渐增大，回路中产生焦耳热，根据功能关系可知：外力做功应等于整个回路中产生的内能与杆获得的动能之和．

所以外力F做的功大于整个电路消耗的电功．

磁场对ab杆作用力的功率等于整个回路消耗的电功率，由于ab杆也有电阻，所以磁场对ab杆作用力的功率大于电阻R上消耗的电功率．

故答案为：大于，大于．

多项选择题

收集计算机数据等资料的原始载体有困难的，可以收集复制件，并注明（）。

A.制作方法

B.制作时间

C.制作人

D.制作程序
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单项选择题

You’re busy filling out the application form for a position you really need, let’s assume you once actually completed a couple of years of college work or even that you completed your degree. Isn’t it tempting to lie just a little, to claim on the form that your diploma represents a Harvard degree Or that you finished an extra couple of years back at State University
More and more people are turning to utter deception like this to land their job or to move ahead in their careers, for personnel officers, like most Americans, value degrees from famous schools. A job applicant may have a good education anyway, but he or she assumes that chances of being hired are better with a diploma from a well-known university. Registrars at most well-known colleges say they deal with deceitful claims like these at the rate of about one per week.
Personnel officers do check up on degrees listed on application forms, then. If it turns out that an applicant is lying, most colleges are reluctant to accuse the applicant directly. One Ivy League school calls them "impostors". Another refers to them as "special cases". One well-known West Coast school, in perhaps the most delicate phrase of all, says that these claims are made by "no such people".
To avoid complete lies, some job-seekers claim that they "attended" or "were associated with" a college or university. After carefully checking, a personnel officer may discover that "attending" means being dismissed after one semester. It may be that "being associated with" a college means that the job-seeker visited his younger brother for a football weekend. One school that keeps records of false claims says that the practice dates back at least to the turn of the century--that’s when they began keeping records, anyhow.
If you don’t want to lie or even stretch the truth, there are companies that will sell you a fake diploma. One company, with officers in New York and on the West Coast, will put your name on a diploma from any number of nonexistent colleges. The price begins at around twenty dollars for a diploma from "Smoot State University". The prices increase rapidly for a degree from the "University of Purdue". As there is no Smoot State and the real school in Indiana is properly called Purdue University, the prices seems rather high for one sheet of paper.

According to the passage, "special cases" refers to cases where ______.

A. students attend a school only part-time
B. students purchase false degrees from commercial firms
C. students never attended a school they listed on their application
D. students attended a famous school
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