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

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

The Law of 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:

 

 

7.1.1-The-Law-of-Magnetism

 

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

 

  • 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

     

 

6.1.1-Hard-and-Soft-Magnetism

 

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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