题目选自2013年厦门市初中毕业及高中阶段各类学校招生考试物理试卷,试题如下:关于影响电磁铁磁性强弱的因素,小鹭有以下猜想:A.通过线圈的电流B.线圈的匝数C.铁芯的形状为了验证猜想,小鹭用两个相同的大铁钉绕成电磁铁甲和乙,还找来一些大头针进行试验,电路如图。(1)将两个电磁铁的线圈串联,是为了研究电磁铁磁性强弱 The topics are taken from the 2013 Xiamen Junior High School graduation and high school entrance examination of various types of physical examination paper, the questions are as follows: On the magnetic susceptibility of electromagnetic factors, small egret has the following conjecture: A. The current through the coil B. The turns of the coil Number C. Iron core shape In order to verify the conjecture, a small heron with two identical iron nails wound into a magnet A and B, but also to find some pins for testing, the circuit shown in Figure. (1) The two electromagnet coils are connected in series to study the magnetic strength of the electromagnet