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Course: Science — Third Preparatory
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Science — Third Preparatory

Science — Third Preparatory

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Science — Third Preparatory 2026/2027

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Unit 1 - Force, Motion, Acceleration and Physical Quantities

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Text lesson

Unit 2 — Electricity and Magnetism

Science — Third Preparatory

Unit 2 — Electricity and Magnetism

3.1 The magnetic effect of electric current

3.1 The magnetic effect of electric current

  • Scrapyards use cranes with huge magnets to lift iron scrap and drop it by switching the magnetism off.
  • How does it work, and how can the strength be controlled?
  • The answer lies in the connection between electricity and magnetism.
  • Oersted’s experiment.
  • Place a compass on a table and wait until its needle settles pointing north.
  • Put a straight wire above the compass, parallel to the needle.
  • Connect the wire in a circuit with a battery and a switch.
  • When the switch is closed, the needle deflects from its original direction; when the circuit is opened, the needle returns.
  • Hans Oersted concluded that an electric current in a wire produces a magnetic field around the wire.
  • This is the magnetic effect of electric current, and it is the basis of the electromagnet, the electric motor and the electric generator.
  • Revision. A magnetic field is the region around a magnet where the effect of its magnetic force can be detected.
  • A compass needle is a small, freely pivoted magnet that points north because of the earth’s magnetic field.
  • Magnetic field lines are imaginary lines that show the direction and strength of a magnetic field.
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