Plotting a Magnetic Field
- In your IGCSE examination you might be asked to describe a method of plotting the magnetic field around a bar magnet.
- There are two principle ways of doing this.
Using Iron Filings
- Place a piece of paper on top of the magnet.
- Gently sprinkle iron filings on top of the paper.
- Now carefully tap the paper to allow the iron filings to settle on the field lines.
Using Plotting Compasses
- Place the magnet on top of a piece of paper.
- Draw a dot at one end of the magnet (near its corner).
- Place a plotting compass next to the dot, so that one end of the needle of the compass points towards the dot.
- Use a pencil to draw a new dot at the other side of the compass needle.
- Now move the compass so that it points towards the new dot, and repeat the above process.
- Keep repeating until you have a chain of dots going from one end of the magnet to the other. Then remove the compass, and link the dots using a smooth curve – the magnetic field line.
- The direction of the field line is the same as the direction of the plotting compass.
- You can now repeat the whole process several times to create several other magnetic field lines.