Question

Permanent magnet can be made by:
1. By holding iron rod in the north-south direction and hammer it repeatedly
2. By placing a ferromagnetic rod in a solenoid and pass a current
3. Both 1 and 2
4. None of these

Answer 1

Correct Answer - Option 3 : Both 1 and 2

CONCEPT:

Permanent magnet:

• Substances that at room temperature retain their ferromagnetic property for a long period of time are called permanent magnets.
• Permanent magnets can be made in the following ways:
  1. By holding an iron rod in the north-south direction and hammer it repeatedly.
  2. By holding a steel rod and stroke it with one end of a bar magnet a large number of times.
  3. An efficient way to make a permanent magnet is to place a ferromagnetic rod in a solenoid and pass a current.
• The hysteresis curve allows us to select suitable materials for permanent magnets.
• The hysteresis curve should be tall and wide for the material that is used to make a permanent magnet.
• The material that is used to make a permanent magnet should have high retentivity and high coercivity.
• Steel is a one-favored choice to make a permanent magnet.
• Other suitable materials for permanent magnets are alnico, cobalt steel, and ticonal.

EXPLANATION:

• From the above, it is clear that the permanent magnets can be made in the following ways:
  1. By holding an iron rod in the north-south direction and hammer it repeatedly.
  2. By holding a steel rod and stroke it with one end of a bar magnet a large number of times.
  3. An efficient way to make a permanent magnet is to place a ferromagnetic rod in a solenoid and pass a current.
• Hence, option 3 is correct.