Credit: RHYS LEWIS, AHS, DECD, UNISA/EQUINOX GRAPHICS/SCIENCE PHOTO LIBRARY

Caption: Animation of the inside of a loudspeaker, showing how the sound is generated by electricity and magnets. Inside the loudspeaker is a magnet, with the south pole surrounded by a coil of wire attached to a paper cone. The north pole of the magnet is outside the wire. When the wire carries a current, I, it induces a magnetic field around the wire. This interacts with the field of the magnet, producing a force that moves the coil, according to Faraday's Law of Induction. The direction of the movement can be predicted using a left-hand rule, demonstrated at bottom left. When the index finger points in the direction of the permanent magnetic field (from north to south), and the middle finger points in the direction of the current, the thumb, held at right angles to the other two digits, points in the direction of the force. This force moves the coil and its attached cone, which generates sound waves in the air. When the current is reversed, the force acts in the opposite direction. Controlling the varying current flowing in the wire therefore controls the vibration of the cone, and hence the sound it produces. See clip K004 3260 for this demonstration with the Australian right-hand rule.

Release details: Model release not required. Property release not required.

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How a loudspeaker works

K004/3261 Rights Managed

Downloadable master

Duration: 00:01:16.15

Frame size: 1920x1080

Frame rate: 25

Audio: No

Format: QuickTime, Photo JPEG 100%, progressive scan, square pixels

File size: 1.1G

Original

Capture format: QuickTime Animation

Codec: PNG

Please contact Science Photo Library if you require the original, or other formats.

 

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