Loudspeakers & Headphones (OCR GCSE Physics A (Gateway Science Suite)): Revision Notes

Loudspeakers work by converting electrical signals into sound. The process is essentially the reverse of how a microphone operates.

How It Works:

• An electrical current flows into a coil of wire within the loudspeaker.
• This coil is placed within a magnetic field, usually generated by a permanent magnet.
• The interaction between the magnetic field of the coil (due to the current) and the magnetic field of the permanent magnet causes the coil to move.
• As the coil moves, it pushes and pulls on the attached cone (or diaphragm).
• The movement of the cone creates pressure variations in the air, which we perceive as sound.

Headphones function similarly to loudspeakers but on a smaller scale. They convert electrical signals into sound waves that can be heard by the listener.

How It Works:

• Electrical Signal: An audio signal (electrical current) is sent through the headphone wires.
• Magnetic Interaction: Inside the headphones, the current flows through a coil of wire, which is located near a permanent magnet.
• Movement of Coil: The interaction between the magnetic field from the current-carrying coil and the magnetic field of the permanent magnet causes the coil to move.
• Vibrating Diaphragm: The coil is attached to a diaphragm (or cone), which vibrates as the coil moves back and forth.
• Sound Waves: These vibrations create pressure waves in the air, which are detected by the ear as sound.