问题 计算题

某同学用多用电表的“×10 Ω”挡测电阻,他的主要操作步骤如下:

A.将选择开关拨至“OFF”位置

B.把表笔插入测试笔插孔中,先把两表笔相接触,旋转调零旋钮,使指针指在电阻刻度的零刻度上

C.把选择开关置于“×10 Ω”挡

D.把两表笔分别与待测电阻的两端相接触并读数这位同学在实验中正确的操作步骤顺序是_________________________.

若该同学在读数时发现指针正指在表盘的“15”刻度处(如图所示),则该电阻的阻值是_______Ω.

答案

CBDA 150

正确的操作步骤是把选择开关置于“×10 Ω”挡;然后把表笔插入测试笔插孔中,先把两表笔相接触,旋转调零旋钮,使指针指在电阻刻度的零刻度上;把两表笔分别与待测电阻的两端相接触后读数;最后将选择开关拨至“OFF”位置.

所以正确的步骤顺序是:C、B、D、A.

欧姆表的读数R=15×10 Ω="150" Ω.

单项选择题

The percentage of immigrants (including those unlawfully present) in the United States has been creeping upward for years. At 12.6 percent, it is now higher than at any point since the mid 1920s. We are not about to go back to the days when Congress openly worried about inferior races polluting America’s bloodstream. But once again we are wondering whether we have too many of the wrong sort of newcomers. Their loudest cites argue that the new wave of immigrants cannot, and indeed do not want to, fit in as previous generations did.

We now know that these racist views were wrong. In time, Italians, Romanians and members of other so called inferior races became exemplary Americans and contributed greatly, in ways too numerous to detail, to the building of this magnificent nation. There is no reason why these new immigrants should not have the same success.

Although children of Mexican immigrants do better, in terms of educational and professional attainment, than their parents, UCLA sociologist Edward Telles has found that the gains don’t continue. Indeed, the fourth generation is marginally worse off than the third. James Jackson, of the University of Michigan, has found a similar rend among black Caribbean immigrants, Telles fears that Mexican Americans may be fated to follow in the footsteps of American blacks—that large parts of the community may become mired in a seemingly state of poverty and underachievement. Like African Americans, Mexican Americans are increasingly relegated to (降入) segregated, substandard schools, and their dropout rate is the highest for any ethnic group in the country.

We have learned much about the foolish idea of excluding people on the presumption of the ethnic/racial inferiority. But what we have not yet learned is how to make the process of Americanization work for all. I am not talking about requiring people to learn English or to adopt American ways; those things happen pretty much on their own, but as arguments about immigration hear up the campaign trail, we also ought to ask some broader question about assimilation, about how to ensure that people, once outsiders, don’t forever remain marginalized within these shores.

That is a much larger question than what should happen with undocumented workers, or how best to secure the border, and it is one that affects not only newcomers but groups that have been here for generations. It will have more impact on our future than where we decide to set the admissions bar for the latest ware of would be Americans. And it would be nice if we finally got the answer right.

According to the author, the burning issue concerning immigration is ().

A.how to deal with people entering the US without documents

B.how to help immigrants to better fit into American society

C.how to stop illegal immigrants from crossing the border

D.how to limit the number of immigrants to enter the US

单项选择题