mag-netic line of force

例句：

1. 1. The magnet attracts ironto it.
   磁铁吸引铁。
2. 2. Themagnetic field of the Earthaffects the weather.
   地球的磁场影响天气。
3. 3. The magnetism of theearth's core is responsible for itsrotation.
   地球核心的磁化作用是其自转的原因。