4.1 Simple phenomena of magnetism (3)
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1.
Question 2
A compass is used to determine the direction of the magnetic field. Describe how you would use a compass to map out the magnetic field around a bar magnet. Explain what you would observe and how you would interpret your results.
To map out the magnetic field around a bar magnet using a compass:
- Place a compass on a flat surface and position it a short distance from the bar magnet.
- Slowly move the compass around the magnet, noting the direction the compass needle points at various locations.
- Mark the direction of the compass needle on a piece of paper as you move.
Observations:
- The compass needle will align itself with the magnetic field at each point.
- The direction of the compass needle will indicate the direction of the magnetic field at that point.
- The closer the compass is to the magnet, the stronger the magnetic field and the more consistently the needle will align.
Interpretation:
By plotting the direction of the compass needle at various points around the magnet, you can draw a series of magnetic field lines. These lines will emerge from the North pole of the magnet and enter the South pole. The density of the lines will indicate the strength of the field.
2.
A bar magnet is placed in a non-uniform magnetic field. Describe how the pattern of the magnetic field lines around the bar magnet will be affected. Explain how this affects the forces acting on the magnet.
When a bar magnet is placed in a non-uniform magnetic field, the pattern of the magnetic field lines around it will be distorted. The field lines will bend and curve as they interact with the external field. Specifically, the magnetic field strength will vary across the magnet's surface. This variation in magnetic field strength will result in non-uniform forces acting on the magnet's poles.
- At the pole facing the stronger part of the external field: The force will be stronger and potentially push the pole towards the stronger field.
- At the pole facing the weaker part of the external field: The force will be weaker and potentially pull the pole away from the weaker field.
The net effect of these non-uniform forces will be to cause the bar magnet to rotate and align itself with the external magnetic field. This is the principle behind magnetic compasses and magnetic separators. The direction of the net force will depend on the relative orientation of the magnet's magnetic field and the external field.
3.
Question 1
A student investigates the forces between magnets. Describe the forces that occur between north poles (N pole), south poles (S pole), and between a magnet and a magnetic material. Use the terms attraction and repulsion, magnetised and unmagnetised in your answer.
When two north poles (N pole) are brought together, they repel each other. Similarly, when two south poles (S pole) are brought together, they also repel. This is because like magnetic poles reject each other.
However, when a north pole and a south pole are brought together, they attract each other. This is because opposite magnetic poles attract.
A magnetic material is magnetised when it is exposed to a strong magnetic field. This aligns the magnetic domains within the material, making it behave like a magnet. A unmagnetised material does not have its magnetic domains aligned and therefore does not exhibit magnetic properties. A magnet will attract a magnetised magnetic material.