一、通电螺线管磁极的判断例 1　试标出图 1中通电螺线管的磁极 .图 1图 2　　解答这类问题的要点是 :先看、后标、再判断 .“先看”即先看清螺线管引入线的哪端接电源正极 .“后标”即是根据引入线所接电源的极性 ,标出螺线管上绕线中的电流方向 .“再判断”即运用安培定则进 1. Judging Example 1 of the Energized Solenoid Pole Figure 1 shows the poles of the energized solenoid in Figure 1. Figure 1 Figure 2 The main points for answering these questions are: look first, postscript, and then judge. “Look first” Look first at which end of the solenoid lead-in line is connected to the positive pole of the power supply. The “postscript” is based on the polarity of the power supply connected to the lead-in line and indicates the current direction in the winding on the solenoid. “Re-judge” is used Ampere