Speakers
claimed by rhester8
The Main Idea
Speakers are devices that are used to translate electrical signals into amplified sounds. Essentially, they have the opposite function of microphones which convert sounds into electrical signals.
How Speakers Work
Speakers are comprised of 3 fundamental parts: a coil, a permanent magnet, and a cone. The coil is positioned near the permanent magnet. It is made of wire and wrapped around metal, so when a current is passed through the device, it creates a magnetic field. In this way, the coil is able to act as an electromagnet. Electrical signals are pulsed into the speaker from an external device (microphone, computer, iPod, etc.) acting as currents and creating a magnetic field from the coil. This magnetic field interacts with the nearby permanent magnet (either repels it or attracts it based on its direction). Because the impulses act as an alternating current, the direction of the current is always changing; therefore, the direction of the magnetic field is changing. Due to the change in direction of the magnetic field, the interactions with the permanent magnet also switch back and forth. For instance, if the magnetic field created by the current initially attracted the permanent magnet, milliseconds later, the current would change directions and the permanent magnet would be repelled by the new, altered magnetic field. This very frequent switch from attraction to repulsion (& visa versa) of the permanent magnet and the coil creates vibrations. The cone of the speaker, usually made of thin paper or plastic, then amplifies these vibrations, therefore increasing their amplitude and volume.
A Mathematical Model
The coil wrapped metal is a solenoid. The formula for the Magnetic Field of a Solenoid is: [math]\displaystyle{ B = {\mu _{0}} \frac{NI}{L} }[/math] Where n is the number of loops in the coil. As shown in the equation, the greater the number of loops, n, the greater the magnetic field created by solenoid.
A Computational Model
Right-Hand Rule: To determine the direction of the magnetic field created by a coil, place your thumb in the direction of the conventional current and your fingers will curl in the direction of the magnetic field.
1.Cone
2.Coil
3.Permanent Magnet
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