4 sentences

1. 磁铁的同极相互排斥。

   cí​tiě de tóng jí xiāng​hù pái​chì.

   Like poles of magnets repel each other.

   Source: Dong Chinese Dictionary

2. 磁铁同性相斥，异性相吸。

   cí​tiě tóng​xìng xiāng​chì, yì​xìng xiāng xī.

   Like poles of a magnet repel each other, while opposite poles attract.

   Source: Dong Chinese Dictionary

3. 磁铁的北极与另一个磁铁的南极相互吸引。

   cí​tiě de běi​jí yǔ lìng yī gè cí​tiě de nán​jí xiāng​hù xī​yǐn.

   The north pole of a magnet attracts the south pole of another magnet.

   Source: Dong Chinese Dictionary

4. 你可以用这块磁铁把黑板上的教学卡片吸住。

   nǐ kě​yǐ yòng zhè kuài cí​tiě bǎ hēi​bǎn shàng de jiào​xué kǎ​piàn xī​zhù.

   You can use this magnet to hold the teaching cards on the blackboard.

   Source: Dong Chinese Dictionary