Edexcel IGCSE Physics: Double Science 复习笔记：6.1.1 Magnetism

Poles of a Magnet

• The ends of a magnet are called poles
• Magnets have two poles: a north and a south

Poles of a Magnet

The Law of Magnetism

• When two magnets are held close together, there will be an attractive or repulsive force between the magnets depending on how they are arranged:

Opposite poles attract; like poles repel

• The Law of Magnetism states that:
  • Two like poles (S and S or N and N) repel each other
  • Two unlike poles (S and N) attract each other

   

• The attraction or repulsion between two magnetic poles is an example of a non-contact force

• Magnetic materials can be soft or hard
• Magnetically soft materials (e.g. iron):
  • Are easy to magnetise
  • Easily lose their magnetism (temporarily magnetised)

   

• Magnetically hard materials (e.g. steel):
  • Are difficult to magnetise
  • Do not easily lose their magnetism (permanently magnetised)

   

• Permanent magnets are made out of magnetically hard materials
• Electromagnets are made out of magnetically soft materials
  • This means that electromagnets can be made magnetic or non-magnetic as an when required

   

A steel pin will be attracted when an electromagnet switches on but not when it switches off. It is always attracted to a permanent magnet 

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