Teach: Magnetic fields

Aims

  • To introduce the concept of magnetism.
  • Sketch magnetic lines of flux for bar magnets, wires, coils and solenoids.
  • Understand the connection between magnetism and current..
  • Use the right hand grip rule.

Observations and common pitfalls

The most difficult thing to get across is the reason why the magnetic North pole of the Earth is in the South. The North pole of a magnet should be called the North seeking pole. I explain to my students that the North pole of the Earth should be called the North seeking pole so if you hung the Earth above the Earth the North pole of the Earth would point South. I don't think this helps.

Physics lab compasses have an annoying tendency to get magnetised the wrong way round, make sure your compasses point north, Geographic north that is.

You need a big current to cause a small compass to rotate, this will trip the circuit breaker on your power supply. I get around this by holding the circuit breaker closed. Probably not good for the power supply.

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