问题 选择题

.某次实验中,李明同学连接了如图所示的电路,若电源电压为6V,且保持不变,电阻R1=8Ω,滑动变阻器R2的最大阻值为10Ω。他所选用的电压表量程为0~3V,电流表量程为0~0.6A。为了保证电路安全,实验中滑动变阻器接入电路的阻值范围是(   )

A.0~2Ω      B.0~8Ω     C.2Ω~8Ω    D.8Ω~10Ω

答案

答案:C

当电流表示数为I1=0.6A时,电阻R1两端电压为U1=I1R1=0.6A×8Ω=4.8V;

滑动变阻器两端的电压U2=U-U1=6V-4.8V=1.2V,所以滑动变阻器连入电路的电阻最小为R===2Ω;当电压表示数最大为U=3V时,R1两端电压为U3=U-U=6V-3V=3V,电路电流为I===0.375A,滑动变阻器接入电路的电阻最大为R===8Ω.故滑动变阻器接入电路的阻值范围是2Ω~8Ω.故选C.

单项选择题
填空题

In America there are no nobles or men of letters, and the common folk mistrust the wealthy. Consequently, (1) form the highest political class, and the most cultivated circle of society. They have therefore (2) by innovation, which adds a conservative interest to their natural taste for (3) . If I were asked where I place the American aristocracy, I should reply (4) that it is not composed of the rich, who are united together by (5) , but that it occupies the judicial bench and the bar.
When I started researching this topic, I found an interesting (6) Legal Reform Now. As the name suggests, this web site is devoted to (7) , and it is definitely concerned about the dominance of lawyers in (8) . There I read an article by a (9) from the University of Wisconsin. One observation the UW article (10) is that the legal profession is the dominant profession of the people (11) to public office. For example, about half our representatives and (12) of our senators are lawyers. No other profession (13) having the same number of people in political office.
Effectively, lawyers form our nation’s (14) organized political constituency in America. Lawyers (15) and lawyers interpret our laws. When judges are appointed, the American Bar Association is the only (16) that is consulted to rate the fitness of potential judicial appointees.
Our nation has been in existence for (17) and lawyers have been this nation’s aristocracy since its (18) . Our system works, but do we really want to have a single profession (19) our nation. Specifically, do we want to have the legal profession in charge (20) , that is something to think about.

In America there are no nobles or men of letters, and the common folk mistrust the wealthy. Consequently, (1) form the highest political class, and the most cultivated circle of society. They have therefore (2) by innovation, which adds a conservative interest to their natural taste for (3) . If I were asked where I place the American aristocracy, I should reply (4) that it is not composed of the rich, who are united together by (5) , but that it occupies the judicial bench and the bar.
When I started researching this topic, I found an interesting (6) Legal Reform Now. As the name suggests, this web site is devoted to (7) , and it is definitely concerned about the dominance of lawyers in (8) . There I read an article by a (9) from the University of Wisconsin. One observation the UW article (10) is that the legal profession is the dominant profession of the people (11) to public office. For example, about half our representatives and (12) of our senators are lawyers. No other profession (13) having the same number of people in political office.
Effectively, lawyers form our nation’s (14) organized political constituency in America. Lawyers (15) and lawyers interpret our laws. When judges are appointed, the American Bar Association is the only (16) that is consulted to rate the fitness of potential judicial appointees.
Our nation has been in existence for (17) and lawyers have been this nation’s aristocracy since its (18) . Our system works, but do we really want to have a single profession (19) our nation. Specifically, do we want to have the legal profession in charge (20) , that is something to think about.