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问题 问答题

在使用万用表的欧姆档测量电阻时，使用前指针已指在左边零刻度，然后将选择开关打至任何倍率的档位，两表笔短接调零时发现，指针始终无法指到电阻零刻度，最多只能向右偏至图1示位置，为了解决问题，下列的哪些做法是可行的：______

A．利用螺丝刀调节机械调零旋纽，使指针偏至电阻零刻度

B．更换新电池．

欧姆表修理好后，为了测定电阻R的阻值，某同学将电键断开，选择适当的倍率并进行调零，然后将红黑表笔接在图2 AB两点间，则其测量值比真实值______（填“偏大”、“偏小”或“相等”）

答案

由于使用前指针已指在左边零刻度，所以方法A不可行；

根据闭合电路欧姆定律可知，若电池已报废使得电动势降低内电阻最大，从而电流过小致使指针始终无法指到电阻零刻度，应更换新电池，

所以方法B可行．

由图2可知，此时欧姆表测量的是待测电阻R与变阻器左半部分的并联电阻，由于并联电阻小于任一支路的电阻，所以测量值比真实值偏小．

故答案为：B，偏小

判断题

如卫生行政部门接到跨辖区的食物中毒事故报告，应通知有关辖区卫生行政部门，并同时向共同的上级人民政府卫生行政部门报告。
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填空题

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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