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问题 计算题

如图甲是某电热器的电路示意图．其中R1=R2=60.5Ω

（1）正常情况下，零线和地线之间的电压为_________V．

（2）电热器有高、低温两档，当旋纽开关拨至触点“1”时，该电热器处于_________，此时电热器消耗的电功率为多少？

（3）有金属外壳的用电器，使用的都是三脚插头和三孔插座，目的是_________．如果请你为这台电热器配备一个三脚插头，如图乙所示，应该将电路图中的E接到插头的_________

（4）为了辨别火线和零线，选用测电笔时，正确的方法是图_________（选填“a”或“b”）．

（5）当电热器在旋钮开关接触点“0”和“2”时的电功率分别为多少？接触点“2”时通电1min产生的热量是多少？

（6）小明想在电路中加一个“倾倒开关”，使电热器被碰倒时能自动断开电路，以免引起火灾．该开关最好应安装在示意图中A、B、C、D、E中的_________．

答案

（1）0；

（2）低温；400W．

（3）金属外壳的用电器漏电时，防止发生触电事故；G

（4）a．

（5）当旋钮开关接触“0”时，电路是断路，电功率为0W；

当旋钮开关接触“2”时，只有R1接入电路，

（6）C

单项选择题

Taiwan police cannot decide whether to treat it as an extremely clever act of stealing or an even cleverer cheat. Either way, it could be the perfect crime, because the criminals are birds homing pigeons!
The crime begins with a telephone message to the owner of a stolen car: if you want the car back, pay up. Then, the ear owner is directed to a park, told where to find a bird cage and how to attach money to the neck of the pigeon inside. Carrying the money in a tiny bag, the pigeon flies off.
There have been at least four such pigeon pick ups in Changwa. What at first seemed like the work of a clever stay at home car thief, however, may in fact be the work of an even lazier and more inventive criminal mind—one that avoids not only collecting money but going out to steal the car in the first place. Police officer Chen says that the criminal probably has pulled a double trick: he gets money for things he cannot possibly return. Instead of stealing cars, he lets someone else do it and then waits for the car owner to place an ad in the newspaper asking for help.
The theory is supported by the fact that, so far, none of the stolen cars have been returned. Also, the amount of money demanded—under 3,000 Taiwanese dollars—seems too little for a car worth many times more.
Demands for pigeon delivered money stopped as soon as the press reported the story. And even if they start again, Chen holds little hope of catching the criminal. "We have more important things to do", he said.

We may infer from the text that the criminal knows how to reach the car owners because ______.

A．he reads the ads in the newspaper
B．he lives in the same neighborhood
C．he has seen the car owners in the park
D．he has trained the pigeons to follow them
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单项选择题

某商场处理有瑕疵的商品，且已向消费者告知，但以下哪批产品按规定还是不能销售的（）。

A、某批服装只是存在扣子不齐的瑕疵

B、某批蚊帐有些许小洞

C、某批剪刀看上去比较陈旧

D、某批饮料超过保质期1天
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