Chapter 36, Problem 46A

An iron bar can be easily magnetized by aligning it with the magnetic field lines of Earth and striking it lightly a few times with a hammer. This works best if the bar is tilted down to match the dip of Earth’s field. The hammering jostles the domains so they can better fall into alignment with Earth’s field. The bar can be demagnetized by striking it when it is in an east—west direction.

To determine

To Explain: An iron bar can be easily magnetized by aligning it with the magnetic field lines of the earth and de-magnetizes by striking it lightly a few times with a hammer.

Explanation of Solution

Introduction: 

A magnet is a material that produces a magnetic field. This magnetic field is invisible but it is an important property of a magnet that causes attraction or repulsion with other magnetic materials such as iron. 

Explanation: 

A simple magnet (iron bar) can easily be magnetized by aligning it with magnetic field lines of the Earth and the bar can easily be demagnetized by striking it when it is in the east-west direction.

When a magnet is in the east-west direction, and struck with a hammer, its magnetic properties will be destroyed due to disorientation of domains.  

Also, one can demagnetize a magnet in different ways such as by hitting on both ends of the magnet using a hammer which causes the ordering in the magnet to be destroyed. Another way is to rub one magnet with another one which should demagnetize one of the magnets.