按如图所示的电路连接各元件后，闭合开关S，、两灯泡都能发光。_爱下问搜题

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问题选择题

按如图所示的电路连接各元件后，闭合开关S，、两灯泡都能发光。在保证灯泡安全的前提下，当滑动变阻器的滑动头向右移动时，下列判断正确的是

A．变亮

B．变暗

C．变亮

D．亮度不变

答案

答案：A

题目分析：当滑片右移时，滑动变阻器接入电阻增大，则总电阻增大，由闭合电路欧姆定律可知总电流减小，而在干路上，所以流过的电流减小，故的变暗；电路总电阻增大，根据欧姆定律可得路端电压增大，而通过的电流减小，即两端的电压减小，所以并联电路两端电压增大，故所在支路的电流增大，所以灯泡变亮；A正确

阅读理解

阅读理解。

This is Mike's bedroom. You can see a desk and a bed in the room. On the desk, there is a backpack

and three books. One is a Chinese book, the other two are English books. There is a clock on the desk,

too. You can see a baseball under the desk. On the bed there is a box. Can you guess (猜) what's in the

box? Ah, it's a new computer game. It's the present (礼物) for Mike's seventh (第七) birthday.

1. Whose (谁的) room is this?

A. May's.

B. Mike's.

C. Simon's

D. Mark's

2. How many (多少) Chinese books are there on the desk?

A. One

B. Two

C. Three

D. Four

3. What's that under the desk?

A. A clock

B. A bed

C. A baseball

D. A notebook

4. What can't (不能) you see on the desk?

A. Book

B. Backpack

C. Computer

D. Clock

5. How old is Mike?

A. 4

B. 5

C. 6

D. 7

单项选择题 A1/A2型题

萌出囊肿位于正在萌出的乳牙或恒牙的（）

A.牙冠表面

B.牙颈部

C.根部

D.根尖部

E.任何部位