Physics 2014 JAMB Past Questions - Question 40: What is the best method of demagnetizing a steel bar magnet?

Correct Answer

D

Explanation

the best method of demagnetizing a steel bar magnet is connecting, alternating current to a solenoid with the bar magnet inside it.To demagnetize a steel bar magnet, you can use a few different methods. Here are a couple of commonly used techniques:

1. Heating: Heat the steel bar magnet to a high temperature and then allow it to cool slowly. This process disrupts the alignment of the magnetic domains within the magnet, causing it to lose its magnetism. However, be cautious not to overheat the magnet, as excessive heat can damage it.

2. Hammering: Another method is to subject the magnet to mechanical shock by repeatedly striking it with a hammer. This disrupts the alignment of the magnetic domains and reduces the magnetism. However, this method can potentially damage the magnet, so it should be used with care.

It's important to note that these methods may not completely demagnetize the magnet, but they can significantly reduce its magnetic strength. If you require a more precise and thorough demagnetization, specialized equipment such as demagnetizing coils or degaussing machines may be necessary.