问题 问答题

如图所示,让金属棒ab水平向右运动时,灵敏电流计指针摆动.此实验装置是研究______的,______机就是利用这种现象制成的.将磁极上下对调,其他不变,观察指针摆动情况,这样操作是为了研究______.

答案

导体ab在磁场中做切割磁感线运动时,电流表的指针摆动说明电路中有电流产生,这种现象就叫电磁感应.所以此装置是研究电磁感应现象的;

利用电磁感应现象制成了发电机;

磁极对调,改变了磁场方向,根据控制变量法的思路可知,这种操作是为了研究感应电流的方向与磁场方向的关系.

故答案为:电磁感应现象;发电;感应电流的方向与磁场方向的关系.

多项选择题
单项选择题

Like many of my generation, I have a weakness for hero worship. At some point, however, we all to question our heroes and our need for them. This leads us to ask: What is a hero

Despite immense differences in cultures, heroes around the world generally share a number of characteristics that instruct and inspire people.

A hero does something worth talking about. A hero has a story of adventure to tell and community who will listen. But a hero goes beyond mere fame.

Heroes serve powers or principles larger than themselves. Like high-voltage transformers, heroes take the energy of higher powers and step it down so that it can be used by ordinary people.

The hero lives a life worthy of imitation. Those who imitate a genuine hero experience life with new depth, enthusiasm, and meaning. A sure test for would-be heroes is what or whom do they serve What are they willing to live and die for The answer or evidence suggests they serve only their own fame, they may be famous persons but not heroes. Madonna and Michael Jackson are famous, but who would claim that their fans find life more abundant

Heroes are catalysts (催化剂) for change. They have a vision from the mountaintop. They have the skill and the charm to move the masses. They create new possibilities. Without Gandhi, India might still be part of the British Empire. Without Rosa Parks and Martin Luther King, Jr., we might still have segregated (隔离的) buses, restaurants, and parks. It may be possible for largescale change to occur without leaders with magnetic personalities, but the pace of change would be slow, the vision uncertain, and the committee meetings endless.

Madonna and Michael Jackson are not considered heroes because ().

A. they are popular only among certain groups of people

B. their performances do not improve their fans morally

C. their primary concern is their own financial interests

D. they are not clear about the principles they should follow