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问题 实验题

某同学对实验室的一个多用电表中的电池进行更换时发现，表内除了一节1.5V的干电池外，还有一个方形的电池（层叠电池）。为了测定该电池的电动势和内电阻，

实验室中提供如下器材：

A．电流表A1（满偏电流10mA，内阻10Ω）；

B．电流表A2（0～0.6～3A，内阻未知）；

C．滑动变阻器R0（0～100Ω，1A）；

D．定值电阻R（阻值990Ω）；

E．开关与导线若干。

（1）该同学根据现有的实验器材，设计了如图a所示的电路，请你按照电路图在图b上用笔画线代替导线完成线路连接。

     

（2）图c为该同学根据上述设计的实验电路测出多组数据并绘出的I1-I2图线（I1为电流表A1的示数，I2为电流表A2的示数），则由图线可以得到被测电池的电动势E＝    V，内阻

r=         Ω。（保留两位有效数字）

答案

(1)       （2） 9.0          10

把图c中图线延长与纵轴相交

本题用电流表与定值电阻串联替代电压表，则9.0mA电流等效电压为，因此电动势为9.0v；

同理8.0mA等效电压为8.0v，6.0mA等效电压为6.0v；=

单项选择题

自1965年到1980年，Indianapolis 500赛车比赛中赛车手的平均年龄和赛车经历逐年增长。这一增长原因是高速赛车手比他们的前辈们活得长了。赛车的安全性能减少了以前能夺走驾驶者生命的冲撞的严重性，它们是Indianapolis 500赛车比赛中车手平均年龄增长的根本原因。下面的哪个，如果正确，最可能成为证明汽车安全性能在重大撞车中保护了车手，是赛车中赛车平均年龄增长的原因( )

A．在1965年到1980年间，快速车道上发生重大事故的年轻车手略多于年长的车手。

B．1985年之前和之后，发生在高速赛车道上的重大事故发生频率相同。

C．在1965年到1980年，试图取得资格参赛Indianapolis 500的车手的平均年龄有轻微下降。

D．1965年之前和之后，在美国高速公路上事故发生的频率相同。
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A Great Friendship


Thomas Jefferson and James Madison met in 1776. Could it have been any other year They worked together starting then to further American Revolution and later to shape the new scheme of government. From the work sprang a friendship perhaps incomparable in intimacy and the trustfulness of collaboration and induration. It lasted 50 years. It included pleasure and utility but (1) and above them, there were shared purpose, a common end (2) an enduring goodness on both sides. Four and a half months (3) he died, when he was ailing, debt-ridden, and worried about his impoverished (4) , Jefferson wrote to his longtime friend. His words and Madison’s reply remind us (5) friends are friends until death. They also remind us that (6) a friendship has a bearing on things larger than the (7) itself, for has there ever been a friendship of (8) public consequence than this one
"The friendship which has subsisted (9) us now half a century, the harmony of our political (10) and pursuits have been sources of constant happiness to me through (11) long period. It’s also been a great solace to me to believe that you’re (12) in vindicating to posterity the course that we’ve pursued for preserving to them, (13) all their purity, their blessings of self-government, (14) we had assisted in acquiring for them. If ever the earth has beheld a (15) of administration conducted with a single and steadfast eye to the general (16) and happiness of those committed to it, one (17) , protected by truth, can never known reproach, it is that to which our (18) have been devoted. To myself you have been a pillar of (19) throughout life. Take care of me when dead and be assured that I (20) leave with you my last affections." A week later Madison replied—"You cannot look back to the long period of our private friendship and political harmony with more affecting recollections than I do. If they are a source of pleasure to you, what aren’t they not to be to me We cannot be deprived of the happy consciousness of the pure devotion to the public good with which we discharge the trust committed to us and I indulge a confidence that sufficient evidence will find in its way to another generation to ensure, after we are gone, whatever of justice may be withheld whilst we are here.\
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