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问题 计算题

如图12—14是某同学设计的一个能够测定油箱内油面高度的装置，油量表是

由学生用电流表改装而成的，滑动变阻器R的金属滑片P是杠杆的一端，当P在a端时电路

中的电流为0.6A，表示油箱已满；当P在b端时电路中的电流为0.1 A，表示油箱内无油．

(1)在改装表盘时，当他选择的滑动变阻器R的最大阻值为50Ω时，他应选择的电源电压值

和R’的阻值是多少?

(2)若油箱的容积为50L，请你按该同学的改装，在电流表盘图12—15上标出油量值为0、40L、50L的刻度位置(滑动变阻器接人的阻值随浮标升降均匀变化；确定40L的位置时要求有运算过程)．

图12—14                  图12—15

(3)你认为他在设计该装置的电路时，在选择器材的过程中应考虑什么问题?并说明理由．

答案

(3)①为保护电流表，选择电源和R’时，电压与R’的比值应小于(或等于)电流表的量程．(或应

考虑当P在a点时电流不超过电流表的量程)②为了提高油量表的灵敏度，应选择在电流表

0～0.6A的量程标注刻度；为了确保使油量在电流表0.1A～0.6A的范围内变化，应考虑电

源电压、R’与R的合理配置．

问答题

The first mention of slavery in the statutes of the English colonies of North America does not occur until after 1660--some forty years after the importation of the first Black people. Lest we think that slavery existed in fact before it did in law, Oscar and Mary Simon assure us that the status of Black people down to the 1660’s was that of servants. (46) A critique of the Simons’ interpretation of why legal slavery did not appear until the 1660’s suggests that assumptions about the relation between slavery and racial prejudice should be reexamined, and that explanations for the different treatment of Black slaves in North and South America should be expanded.
(47) The Simons explain the appearance of legal slavery by contending that, during the 1660’s, the position of White servants was improving relative to that of Black servants. Thus, the Simons argue, Black and White servants, heretofore treated alike, each attained a different status. There are, however, important objections to this argument. First, the Simons cannot adequately demonstrate that the White servant’s position was improving during and after the 1660’s; several acts of the Maryland and Virginia legislatures indicate otherwise. Another flaw in the Simons’ interpretation is their assumption that prior to the establishment of legal slavery there was no discrimination against Black people. It is true that before the 1660’s Black people were rarely called slaves. But this should not overshadow evidence from the 1630’s on that points to racial discrimination without using the term slavery. Such discrimination sometimes stopped short of lifetime servitude or inherited status--the two attributes of true slavery--yet in other cases it included both. (48) The Simons’ argument excludes the real possibility that Black people in the English colonies were never treated as the equals of White people.
This possibility has important ramifications. (49) If from the outset Black people were discriminated against, then legal slavery should be viewed as a reflection and an extension of racial prejudice rather than, as many historians including the Simons have argued, the cause of prejudice. In addition, the existence of discrimination before the advent of legal slavery offers a further explanation for the harsher treatment of Black slaves in North than in South America. (50) Frey and Terry have rightly argued that the lack of certain traditions in North America--such as a Roman conception of slavery and a Roman Catholic emphasis on equality--explains why the treatment of Black slaves was more severe there than in the Spanish and Portuguese colonies of South America. But this cannot be the whole explanation since it is merely negative, based only on a lack of something.
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判断题

在社会主义建设中，把马克思主义基本原理和中国实际结合起来，排除教条主义和经验主义的干扰，推进中国特色社会主义建设事业。它的哲学依据就是矛盾的特殊性与普遍性的关系原理。( )
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