3、右手定则；

2、感应电流的方向；

1、电磁感应现象；

198．Since we are social beings, the quality of our lives depends in large measure on our interpersonal relationships.

197．Americans are proud of their variety and individuality, yet they love and respect few things more than a uniform, whether it is the uniform of an elevator operator or the uniform of a five-star general.

196．But for many, the fact that poor people are able to support themselves almost as well without government aid as they did with it is in itself a huge victory.

195．While still in its early stages, welfare reform has already been judged a great success in many states at least in getting people off welfare.

194．If FIFA, football’s international ruling body, wants to improve the standard of refereeing at the next World Cup, it should encourage referees to keep their eyes on the action from a distance, rather than rushing to keep up with the ball, the researcher argues.

193．Why does cream go bad faster than butter? Some researchers think they have the answer, and it comes down to the structure of the food, not its chemical composition-a finding that could help rid some processed foods of chemical preservatives.

192．These ads were strategically placed among family-oriented TV shows and programs involving nature and America in order to most effectively reach target audiences.