电磁铁
Electromagnets
描述电流的磁效应（通电导线会产生磁场），并探究电磁铁的强弱如何取决于电流大小、线圈匝数和铁芯材料。
Describe the magnetic effect of an electric current (a current-carrying wire produces a magnetic field), and investigate how the strength of an electromagnet depends on current, number of coil turns, and core material
学习证据 / Evidence
- 能描述通电导线周围会产生环形磁场。
- 能列出影响电磁铁强弱的三个因素：电流大小、线圈匝数和铁芯材料。
- 能解释为什么电磁铁可以通断电来控制磁性，而永磁铁不能这样。
- Describes that a current-carrying wire produces a circular magnetic field
- Lists three factors that affect electromagnet strength: current size, number of coil turns, and core material
- Explains why an electromagnet can be switched on and off, unlike a permanent magnet
评估问题 / Assessment
如果{{name}}用一节电池、导线和一枚铁钉制作了一个电磁铁，ta能说出两种让电磁铁吸起更多回形针的方法吗？并且能解释为什么断开电路后电磁铁就不再工作？
If {{name}} built an electromagnet using a battery, wire, and iron nail, could they describe two ways to make it pick up more paperclips — and explain why it stops working when the circuit is switched off?