题目内容

【题目】有两只电压表V1和V2，量程已知，电阻未知。另有一干电池，它的内阻不能忽略，但不知等于多少，其电动势数值不超出电压表的量程，干电池不许拆开。现给你上述两只电压表、一个开关S和若干导线，请设计一个测量上述干电池电动势E的实验方案。

（1）画出测量电路图。

（2）实验中应测定的物理量是：________。

（3）以测得的物理量为已知量，导出计算干电池电动势的公式E＝________。

【答案】（1）如图

（2）S闭合时电压表V1的示数U1

S断开时电压表V1、V2的示数U1′、U2′

（3）

【解析】（1）电路图如下

（2）S闭合时，V1示数为U1；S断开时，V1、V2的示数分别为U1′和U2′。

（3）设V1表的内电阻为RV，由闭合电路欧姆定律

E＝U1＋r，E＝U1′＋U2′＋r

解得：E＝

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Every day, in all kinds of weather, a lot of people go jogging (running slowly). Why has jogging became so popular? Most people start jogging because you hear it is a very good form of exercise. Jogging makes the heart strong and help people control their weight and stay slim. If you jog regular, you needn’t take pills or skip meals to lose weight. Jogging can also make you to feel better.

Donald Robbins, he is 42 years old and works in an office, began jogging a few years later because he felt he was overweight. At first he could only run 300 metres, and two years later, he ran a marathon — over 42 kilometres.

Do you jog? If you do, be sure to ask your doctor on advice. Does jogging cost much? Almost nothing. But it is very important to have a pair of shoe that are made especially for jogging. If not, when you run on hard ground for a long time it may cause your feet to hurt.

【题目】短文改错

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1. 每处错误及其修改均仅限一词；

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The summer holiday is coming. Our class has a discussion about what to do during the holiday.
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In my opinion, it would be much good to stay at home, for I can do how I like, such as reading books, watching TV, and help my parents with the housework.

【题目】如图所示是电饭煲的电路图，S1是一个控温开关，手动闭合后，当此开关温度达到居里点（103 ℃）时，会自动断开。S2是一个自动控温开关，当温度低于60 ℃时会自动闭合；温度高于80 ℃时，会自动断开。红灯是加热时的指示灯，黄灯是保温时的指示灯。分流电阻R1＝R2＝500 Ω，加热电阻丝R3＝50 Ω，两灯电阻不计。

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【题目】短文改错（每小题1分，满分10分）

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【题目】B

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Soon Katharine returned to Washington and got a job editing letters to the editor of her father’s newspaper. In 1946, her husband Philip Graham became publisher of The Washington Post. When she was 46, her husband died, leaving Katharine Graham four children to raise and a newspaper to operate.

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