The polarity of an unmarked horse shoe magnet can be determined by using

The polarity of an unmarked horse shoe magnet can be determined using a magnetic compass because a compass needle is itself a small magnet with defined North and South poles [3]. According to the fundamental law of magnetism, unlike poles attract and like poles repel [3]. When a compass is placed near the ends of the unmarked magnet, the South pole of the compass needle will be attracted to the North pole of the magnet, while the North pole of the needle will point toward the magnet's South pole [2]. This interaction allows for the clear identification of the magnet's polarity [1]. Other options like a charged glass rod or an electroscope are used for detecting electric charges rather than magnetic poles. Using another unmarked bar magnet would not work as neither magnet has known poles to serve as a reference.

Sources

1. [3] Science , class X (NCERT 2025 ed.) > Chapter 12: Magnetic Effects of Electric Current > What you have learnt > p. 206
2. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 4: Electricity: Magnetic and Heating Effects > Activity 4.4: Let us investigate > p. 51
3. [2] Science , class X (NCERT 2025 ed.) > Chapter 12: Magnetic Effects of Electric Current > Activity 12.3 > p. 196