Revision as of 04:48, 13 April 2008

Outcomes

• Pupils understand that magnets exert forces on each other and other magentic materials. These forces can be attraction or repulsion.
• Pupils can understand how to plot a magnetic field around:
• one bar magnet
• two bar magnets, attracting and repelling.
• Pupils understand that the direction of a magnetic field line indicates the direction of the force on a tiny north pole magnet placed in the field at that point.
• Pupils can see that a uniform field can be created between to attracting bar magnets.

Specification References

6.2 recall that magnets repel and atract other magnets, and attract magnetic substances.

6.3 recall the properties of magnetically hard and soft materials

6.4 understand the term 'magnetic field line'

6.5 understand that magnetism is induced in some materials when they are placed in a magnetic field.

6.6 sketch and recognise the magnetic field pattern for a permanent bar magnet and that between two bar magnets

6.7 know how to use two permanent magents to produce a unifrom magnetic field.

Starter

Recall from lower school work that magnets have both north and south poles. Talk about idea of a 'magnetic force field'. Forces 'push' or 'pull' : 'attract' or repel'.

Starter practical: Use mini turntables or upturned watchglasses to show that N and N repel, S and S repel but N and S attract.

Main Body of Lesson

How do we plot this force field when we cannot see it? Introduce idea that forces have direction and we plot force fields by placing a small north pole in the magnetic field of the bar magnet. We draw an arrow to show the direction of the force: Arrow shos direction of force on a tiny north pole placed at that point.

Prediction: Students to draw a bar magnet and, suing the above principle, predict the shape of the field around a bar magnet. You will need to do a field line for them to start them off.

Practical: Using plotting compasses to plot magnetic force field around:

• a single bar magnet
• two bar magnets repelling
• two bar magnets attracting

Check whether the prediction was correct.

Plenary

What you you notice about the shape of the magnetic field between the attracting bar magnets?

• the magnetic field lines are closer togeter = stronger magnetic field
• the magnetic field lines are parallel = uniform magnetic field pattern

Extension:

• What do you notice about the shape of the magnetic field between the repelling magnets?

The is a spot where there is not magneic field = neuatral point.

Homework

Research into where magnets are uses in everyday life. 3 examples with explanations.

Additional Information

Resources Required

bar magnets plotting compasses small frictionless tunrtables or upturned watchglasses

Textbook References

Website References

Skills Addressed

Prediction of experimental outcome.

Safety/Hazards

Notes

Students find understanding magnetic fields easy if the idea about direction of field lines is fullu understood. Therefore key point of lesson is:

• Pupils understand that the direction of a magnetic field line indicates the direction of the force on a tiny north pole magnet placed in the field at that point.