AQA GCSE Physics

Revision Notes

7.2.5 Loudspeakers & Headphones

Higher Tier Only

Loudspeakers & Headphones

  • Loudspeakers and headphones convert electrical signals into sound
    • They work due to the motor effect
  • A loudspeaker consists of a coil of wire which is wrapped around one pole of a permanent magnet

loudspeaker-cross-section, IGCSE & GCSE Physics revision notes

Diagram showing a cross-section of a loudspeaker

  • An alternating current passes through the coil of the loudspeaker
    • This creates a changing magnetic field around the coil
  • As the current is constantly changing direction, the direction of the magnetic field will be constantly changing
  • The magnetic field produced around the coil interacts with the field from the permanent magnet
  • The interacting magnetic fields will exert a force on the coil
    • The direction of the force at any instant can be determined using Fleming’s left-hand rule
  • As the magnetic field is constantly changing direction, the force exerted on the coil will constantly change direction
    • This makes the coil oscillate
  • The oscillating coil causes the speaker cone to oscillate
    • This makes the air oscillate, creating sound waves

Exam Tip

The explanation of the loudspeaker is very similar to the explanation of a motor, however direct current is used in a d.c motor and alternating current is used in a loudspeaker or headphone. You need to learn how both work.

When explaining how a loudspeaker works remember to refer to the alternating current and the changing magnetic field that it creates.

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Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.

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