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问题 多选题

如图所示，R1为滑动变阻器，R2、R3为定值电阻，r为电源内阻．闭合开关S后，在滑动触头P由a端滑向b端的过程中，表述正确的是（　　）

A．路端电压变小

B．电流表的示数变大

C．电源内阻消耗的功率变小

D．电源输出功率可能变大

答案

A、滑片向b端滑动，则滑动变阻器接入电阻减小，故电路中总电阻减小；由闭合电路欧姆定律可知，电路中电流增大；则内压增大，故路端电压减小，故A正确；

B、因R3两端的电压增大，路端电压减小，故R2中的电流减小，故B错误；

C、电源内阻消耗的功率P=I2r，因电流增大，故内电阻消耗的功率增大，故C错误；

D、电流输出的功率当内阻与外阻相等时最大，而本题中不确定内外阻的大小关系，故电源的输出功率有增大的可能，故D正确；

故选AD．

阅读理解

根据短文内容，判断句子正（Ｔ）误（Ｆ）。

     Many children love junk food. It's bad for their health. Their parents don't want them to eat too much junk

food. Although they know it's not a good habit, they still eat it. Some of them eat kind of food every day. Some

only once or twice a week.

     Paul is kind of unhealthy. He hardly ever exercises. He eats lots of junk food because he loves it. When he

has money, he'll buy junk food. His parents worry about him. But he says, "Maybe I'm not very healthy, but I

enjoy myself."

( )1 Few children love junk food.

(     )2 Many parents want their children to eat junk food.

(     )3 Children know it's a bad habit to eat junk food.

(     )4. Paul is very healthy.

( )5. Paul often borrows money to buy junk food.

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单项选择题

我国产业安全面临的突出问题，主要是在技术密集型产业中，核心技术大多依赖外国公司，在国际分工体系中处于劣势地位。因此，增强我国产业安全的主要途径应该是( )。

A．增强自主创新能力
B．使我国GDP持续快速增长
C．依靠劳动力价格的优势
D．依靠科技引进和利用外资
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