Plotting magnetic field lines
- In your IGCSE examination, you might be asked to describe a method of plotting the magnetic field around a bar magnet
- There are two principal ways of doing this:
- using iron filings
- using plotting compasses
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
Magnetic field lines using iron filings
Iron filings can be used to plot a magnetic field
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 on 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. This is the magnetic field line
- The direction of the field lines go from the north pole to the south pole of the magnet.
- This is the same as the direction of the north arrow on the plotting compass, which points towards the south pole
- Repeat the process to create other magnetic field lines around the bar magnet
Using a compass to create magnetic field lines
Compasses can be used to plot the magnetic field around a bar magnet
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