问题 选择题

如图所示,要使流过灵敏电流计的电流反向,下列措施中可行的是(  )

①只将磁场反向;

②只将线圈的运动方向反向;

③同时将磁场和线圈的运动方向反向;

④增加磁铁的磁性或线圈匝数.

A.①②

B.②③

C.①③

D.①④

答案

要使流过灵敏电流计的电流反向,就是要改变感应电流的方向;

①只将磁场反向,就可以改变感应电流的方向,从而使灵敏电流计的电流反向;

②只将线圈的运动方向改变,就会改变感应电流的方向,从而使灵敏电流计的电流反向;

③同时改变磁场方向和线圈的运动方向,感应电流的方向时不变的;

④增加磁铁的磁性或线圈匝数,只能是电流的大小,不能改变感应电流的方向.

故选A.

阅读理解

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Is there anything more important than health? I don’t think so.“Health is the greatest wealth,” wise people say. __小题1:___

If you have a headache, toothache, backache, or bad pain in the stomach, if you complain of a bad cough, or if you suffer from high or low blood pressure, I think you go to the doctor.

The doctor will examine your throat, test your blood pressure, take your temperature, sound your heart and lungs, check your teeth or have your chest X-rayed. __小题2:___The only thing you have to do is to follow his advice.

__小题3:___

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A month later the gentleman came into the doctor’s office.__小题5:__He thanked the doctor and said that he had never felt a healthier man.

“But you know, doctor,” he said, “it’s not easy to begin smoking at my age”

A.He also advised him to eat a lot of meat, drink two glasses of red wine every day and take long walks.

B.You can’t be good at your studies or work well when you are ill.

C.After that he will advise some treatment or some medicine.

D.All these will cost a lot of money. E.He looked cheerful and happy.

F.He was more worried about his illness.

G.Speaking about doctor’s advice, I can’t help telling you a funny story.

多项选择题