题干

根据图中通电螺旋管的N极,请在图中标出小磁针的N极和电源的+极.

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答案(点此获取答案解析)

解:已知螺线管的上端为N极,根据磁极间的相互作用可知,小磁针的上端为S极,下端为N极,

根据线圈的绕向利用安培定则可以确定螺线管中电流是从螺线管的下端流入上端流出.则电源的上端为负极,下端为正极.

如下图所示:

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    Car-hailing company DiDi signed an agreement with TAL Education Group to provide free online courses for the children of taxi drivers. The courses, worth 30 million yuan, cover all subjects from primary to high school. Children can study courses at home, saving parents' time to spend or pick up children from off-line after-school classes.

    According to Zhu Jingshi, vice president of DiDi, all 153 million registered (注册) taxi drivers of DiDi can ask for the courses on the company's mobile app. The car-hailing company will evaluate (评价) the drivers and provide courses on the basis of the time they became registered drivers with the company, the number of passengers served and evaluation from passengers.

    The health and education of children have remained top priorities of Chinese parents, including taxi drivers. A survey done by DiDi and TAL showed that although the average monthly income (平均月收入) of taxi drivers is only 6000 yuan, many would like to pay 40 percent of their income for their children's education.

    The survey found that most taxi drivers were born in the 1970s and 1980s and worked seven days a week. More than 70 percent of them have children under 18 but very few have time to be with family and children. Only 8 percent of them said they had guided their children in doing homework. Because of these, 60 percent of drivers hope their children could receive the guidance from professional services.