Final answer:
To make a compass, magnetize a needle with a bar magnet, float it on a cork in water, and it will align with Earth's magnetic field. Iron filings can help visualize the magnetic field and interactions between magnets. The magnetic field around permanent magnets is due to aligned magnetic domains.
Step-by-step explanation:
To make a compass using a bar magnet, a needle, a cork, and a bowl full of water, start by magnetizing the needle. Stroke the needle with one end of the bar magnet — from the eye to the point — around 30 times. This aligns the magnetic domains within the needle in one direction, effectively turning it into a magnet. Next, push the needle through a small piece of cork, which will serve as a flotation device. Finally, place the cork and needle assembly on the surface of the water in the bowl. The magnetized needle will align itself with the Earth's magnetic field, with one end pointing north and the other pointing south, functioning as a basic compass.
The pattern of iron filings can be used to visualize the magnetic field of bar magnets. By sprinkling iron filings over a piece of paper placed above a bar magnet, you can observe the alignment of the filings in the shape of the field — showing the north and south poles and the field lines that emerge from one pole and enter the other. When two bar magnets are placed close to each other, the iron filings will show patterns of attraction or repulsion, depending on the poles facing each other. This visual experiment helps to understand magnetic fields and interactions between magnets.
In conclusion, the magnetic field around permanent magnets is a result of the alignment of magnetic domains within the material, which creates a region where magnetic forces can be exerted.