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Boundless Physics
Induction, AC Circuits, and Electrical Technologies
Applications of Induction and EM Waves
Physics Textbooks Boundless Physics Induction, AC Circuits, and Electrical Technologies Applications of Induction and EM Waves
Physics Textbooks Boundless Physics Induction, AC Circuits, and Electrical Technologies
Physics Textbooks Boundless Physics
Physics Textbooks
Physics
Concept Version 7
Created by Boundless

Sound Systems, Computer Memory, Seismograph, GFCI

Inductance is used in the operation of many modern devices, such as speakers, memory, seismographs and GRCIs.

Learning Objective

  • Discuss the use of inductance in modern devices


Key Points

    • The microphone works by induction, as the vibrating membrane induces an emf in a coil.
    • A speaker produces sound by induction as varying magnetic forces move a speaker diaphragm, producing air motion that produces sound.
    • Computer memory is stored by inducing signals on read/write heads.
    • GFCIs induce a current to oppose sudden increases in current in a circuit, thus preventing possible electrocution.

Term

  • amplifier

    An appliance or circuit that increases the strength of a weak electrical signal without changing the other characteristics of the signal.


Full Text

Inductors have many uses in modern electronics. In a sound system, sound can be transmitted from a microphone to a speaker (shown in ). The microphone works by induction, as the vibrating membrane induces an emf in a coil. That "signal" is then transmitted to an amplifier and then to a speaker. The speaker is then driven by modulated electrical currents (produced by an amplifier) that pass through and magnetize (by inductance) a speaker coil of copper wire, creating a magnetic field. Thus, the electrical current variations that pass through the speaker are converted to varying magnetic forces, which move the speaker diaphragm, forcing the driver to produce air motion that is similar to the original signal from the amplifier.

A simple, modern speaker.

A speaker with magnet and coils that is used to produce sound.

Inductance in modern electronics is also used in computer memory. Magnetic storage uses different patterns of magnetization on a magnetically coated surface to store information. Differently magnetized areas on tape (or disk) induce signals on "read-write" heads, from which the information is later accessed.

Another application is the seismograph—an instrument for detecting and recording the intensity, direction and duration of ground movement. It contains a fixed coil and a magnet hung on a spring (or vice versa). These "record" the current induced when the Earth shakes.

A ground fault circuit interrupter (GFCI) provides additional safety (that circuit breakers cannot) by stopping the current in a shorted-out circuit. This is done by inductance. If a GFCI detects that there is a leakage of current, it produces an EMF and a current in the opposite direction of the original current.

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