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问题 实验题

利用如图电路，探究“导体电阻的大小与哪些因素有关”。图中甲、乙、丙是镍铬合金丝，甲、乙长度相同，乙、丙粗细相同。实验中，根据                判断接入M、N两点间电阻的大小，探究导体电阻与其横截面积的关系时应选用的电阻丝是        。如果选择乙和丙来做实验，还可以探究导体电阻的大小与      的关系。

答案

电流大小  甲和乙 导体长度

题目分析：实验中根据电流表的示数确定电阻的大小，当探究导体电阻与其横截面积的关系时，保持长度和材料相等，改变横截面积的大小，所以选甲、乙；若选乙和丙，它们的裁量相等，横截面积相同，长度不同，探究电阻的大小和导体长度的关系。

点评：解决本题的关键是熟知控制变量法在实验中的应用。

选择题

某二元酸（化学式用H2A表示）在水中的电离方程式是：H2A==H++HA.

HAH++A2－，回答下列问题：

（1）Na2A溶液呈    （填“酸性”.“中性”或“碱性”），理由是：             

                               （用离子方程式说明）

NaHA溶液呈    （填“酸性”.“中性”或“碱性”），理由是：                 

                                      。

（2）已知0.1mol/LNaHA溶液的pH=2，则0.1mol/L的H2A溶液中氢离子的物质的量浓度        0.11mol/L（填“<”.“>”或“=”）理由是：                

                              ______    。

（3）0.1mol/LNaHA溶液中各种离子浓度由大到小的顺序是：                  

                              。
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单项选择题

Comparisons were drawn between the development of television in the 20th century and the diffusion of printing in the 15th and 16th centuries. Yet much had happened (91) . As was discussed before, it was not (92) the 19th century that the newspaper became the dominant pree-leetronie (93) , following in the wake of the pamphlet and the book and in the (94) of the periodical. It was during the same time that the communications revolution (95) up, beginning with transport, the railway, and leading (96) through the telegraph, the telephone, radio, and motion pictures (97) the 20th-eentury world of the motor ear and the airplane. Not everyone sees that process in (98) . It is important to do so.
It is generally recognized, (99) , that the introduction of the computer in the early 20th century, (100) by the invention of the integrated circuit during the 1960s, radically changed the process, (101) its impact on the media was not immediately (102) . As time went by, computers became smaller and more powerful, and they became "personal" too, as well as (103) , with display becoming sharper and storage (104) increasing. They were thought of, like people, (105) generations, with the distance between generations much (106)
It was within the computer age that the term" information society" began to be widely used to describe the (107) within which we now live. The communications revolution has (108) both work and leisure and how we think and feel both about place and time, but there have been (109) views about its economic, political, social and cultural implications. "Benefits" have been weighed (110) "harmful" outcomes. And generalizations have proved difficult.

A．by means of

B．in terms of

C．with regard to

D．in line with
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