为了探究电磁铁的磁性强弱与哪些因素有关，某同学使用两个相同的大铁钉绕成电磁铁A和B，还找来一些大头针进行实验，电路如图所示。
（1）将两个电磁铁的线圈串联是为了研究电磁铁磁性强弱与______的关系（选填“电流”或“匝数”）；
（2）实验中要通过观察______，来判断电磁铁磁性的强弱。
（1）匝数 （2）电磁铁能够吸起的大头针的数量
题目分析：两只电磁铁是串联的，所以电流相同，只有线圈的匝数是不同的，据此来做出判断；电磁铁吸引的大头针数量越多，电磁铁的磁性越强，这里是采用了转换法的思想．
（1）读图可知，两只电磁铁是串联在电路中的，所以流经它们的电流是相同时，同时还可以看到，它们线圈的匝数是不同的，因此，本实验研究的是电磁铁磁性强弱与匝数的关系；
（2）磁性的强弱无法用肉眼直接观察，因此，可借助观察电磁铁能够吸起的大头针的数量来判断其磁性的强弱，这属于转换法的应用。
| Teachers need to be aware of the emotional, intellectual, and physical changes that young adults experience. And they also need to give serious (51) to how they can best adapt them selves to such changes. Growing bodies need movement and (52) , but not just in ways that emphasize competition. (53) they are adjusting to their new bodies and a whole host of new intellectual and emotional challenges, teenagers are especially self-conscious and need the (54) that comes from achieving success and knowing that their accomplishments are (55) by others. However, the typical teenage lifestyle is already filled with so much competition that it would be (56) to plan activities in which there are more winners than losers, for example, publishing newsletters with many student-written book reviews, (57) student artwork, and sponsoring book discussion clubs. A variety of small clubs can provide (58) opportunities for leadership, as well as for practice in successful (59) dynamics. Making friends is extremely important to teenagers, and many shy students need the (60) of some kind of organization with a supportive adult barely visible in the background. |
A．improper
B．risky
C．fair
D．wise