题干

法拉第首先提出用电场线形象生动地描绘电场,如图所示为点电荷a、b所形成电场的电场线分布图(箭头未标出),在M点处放置一个电荷量大小为q的负试探点电荷,受到的电场力大小为F,以下说法中正确的是(   )

A:由电场线分布图可知M点处的场强比N点处场强大

B:a、b为异种电荷,a的电荷量小于b的电荷量

C:M点处的场强大小为Fq,方向与所受电场力方向相同

D:如果M点处的点电荷电量变为2q,该处场强将变为F2q

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答案(点此获取答案解析)

B

同类题2

请用适当的词完成下面的短文, 补充所缺的单词。每个空只能填写一个形式正确,意义相符的单词。

    If you pay a visit to Liu Hasheng's restaurant in Harbin, you will find 18 robots there. They are ready to serve you and ____ sure that your dining experience is perfect. After the visit, you can tell others that robots serving customers isn't a dream any more.

    It's wonderful to see ____ the 18 robots work in the restaurant. The wonder starts when you walk in. You ‘ll see a robot come up and say, "Earth person, hello! ____ to the Robot Restaurant." When you have ordered your ____, the robots in the kitchen begin to do the cooking. After the food is ____, a robot waiter will glide(滑行) out of the kitchen to serve you with the meal you've ordered. And as customers enjoy their delicious food, a robot ____lovely songs for them.

    You may ask, "Where did all these robots come ____?" Liu said they were designed(设计) and ____ by the Harbin Haohai Robot Company. Liu said he invested(投资) 5 million yuan in the restaurant, with ____ robot costing 200,000 yuan to 300,000 yuan. And the whole robot team is managed by the workers in the computer room.

    After a busy day, all the robots will go for a "meal", which is electricity. After 5 hours, the robots can continue their work for a day. The restaurant now provides a menu ____ more than 30 dishes(菜肴), and the average(平均) cost for a dinner is about 40 to 50 yuan. Do you want to go and have a try in this restaurant?

同类题4

阅读理解

    Diet Coke, diet Pepsi, diet pills, no-fat diet, vegetable diet… We are surrounded by the word “diet” everywhere we look and listen. We have so easily been attracted by the promise and potential of diet products that we have stopped thinking about what diet products are doing to us. We are paying for products that harm us psychologically (心理) and physically.

    Diet products greatly weaken us psychologically. On one level, we are not allowing our brain to admit that our weight problems lie not in actually losing the weight, but in controlling the amount of fatty, high-calorie, unhealthy foods. Diet products allow us to jump over the thinking stage and go straight for the scale(秤) instead. All we have to do is to recognize the word “diet” in food labels.

    On another level, diet products have greater psychological effects. Every time we have a zero-calorie drink, we are telling ourselves without our awareness that we don't have to work to get results. Diet products make people believe that gain comes without pain, and that life can be without struggle.

    The danger of diet products lies not only in the psychological effects they have on us, but also in the physical harm that they cause. Diet foods can indirectly harm our bodies because eating them instead of healthy foods means we are preventing our bodies from having basic nutrients. Diet foods and diet pills contain zero calorie only because the diet industry has created chemicals to produce these wonder products. Diet products may not be nutritional, and the chemicals that go into diet products are possibly dangerous in the future.

    Now that we are aware of the effects that diet products have on us, it is time to seriously think about buying them. Losing weight lies in the power of minds, not in the power of chemicals. Once we realize this, we will be much better able to resist diet products, and therefore prevent the psychological harm that comes from using them.