Q. Consider the following materials:

1. Steel
2. Copper
3. Aluminium
4. Iron

Which of the above are commonly used in the manufacture of permanent magnets?
Answer: Only 1 and 4
Notes: Permanent magnets are made from ferromagnetic materials. Steel (an alloy containing iron) and pure iron are commonly used due to their strong magnetic properties. Copper and aluminium are non-magnetic materials and are not used for making permanent magnets. Thus, only statements 1 and 4 are correct.