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问题 多选题

下列有关磁感应强度的说法正确的是（　　）

A．一小段通电导线放在磁场中某处，如果受到的磁场力为零，该处的磁感应强度不一定为零

B．把一小磁针放在磁场中某处，如果小磁针北极受到的磁场力为零，该处的磁感应强度一定为零

C．根据公式B=

F
IL
可知，放置在磁场中1m长的通电直导线，通过1A的电流，如果受到的磁场力为1N，则该处的磁感应强度就是1T

D．磁场中某处的磁感应强度B的方向跟电流在该处受到的磁场力F的方向一致

答案

A、小段通电导线平行放在某处不受磁场力作用，则该处的磁感应强度不一定为零，可能导线与磁场平行放置，故A正确；

B、把一小磁针放在磁场中某处，如果小磁针北极受到的磁场力为零，该处的磁感应强度一定为零，故B正确；

C、磁感应强度B=

F
IL
只是定义式，它的大小取决于场源以及磁场中的位置，与F、I、L以及通电导线在磁场中的取向无关，只有垂直放置时在磁场中某处受到的磁场力为F，该处磁感应强度的大小一定是
F
IL
．故C错误；

D、根据左手定则可知，磁场中某处的磁感应强度B的方向跟电流在该处受到的磁场力F的方向垂直．故D错误；

故选：AB

单项选择题 A1/A2型题

帕金森病的发病机制与黑质和纹状体内哪种神经递质明显减少有关（）

A.多巴胺

B.乙酰胆碱

C.5-羟色胺

D.肾上腺素

E.γ-氨基丁酸
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听力题

Not many years ago， a wealthy and rather strange old man named Johnson lived a__1___ in a village in the south of England. He had m___2___a lot of money in trading with foreign countries. When he was seventy-five， he gave ￡ 12，000 to the village s____3___ to buy land and equipment for a children’s playground。

As a result of his kindness， many people came to visit him. A__4_____them was a newspaperman. During their talk， Johnson remarked that he was seventy-five and expected to live to be a h___5___. The newspaperman asked him how he managed to be healthy at seventy—five. Johnson had a sense of h__6___.  He liked whisky and drank some each day. “I have an injection （注射） in my neck e___7__ evening.”he told the newspaperman， thinking of his evening glass of whisky.

The newspaperman did not understand what Johnson m__8___. In his newspaper he r____9___that Johnson was seventy-five and had a daily injection in his neck. Within a week Johnson received thousands of letters from all over Britain， asking him for the s__10___ of his daily injection.
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