Applications of Induction

Some of the Many Applications of Induction

Ground Fault Circuit Interrupter

Seismograph

Microphone

Ground Fault Circuit Interupter (GFCI)

ð Circuit breakers are designed primarily to protect equipment.

ð GFCIs are designed to protect humans.

ð The are designed to "trip" before levels at which circuit breakers respond

ð They can typically respond to currrent as small as 5 mA

ð The GFCI constantly monitors electricity flowing in a circuit, to sense any loss of current.

ð If the current flowing through the circuit differs by a small amount from that returning, the GFCI quickly switches off power to that circuit.

ð In homes built to comply with the National Electrical Code (the Code), GFCI protection is required for

        Ø most outdoor receptacles (since 1973)
        Ø bathroom receptacle circuits (since 1975)
        Ø garage wall outlets (since 1978)
        Ø kitchen receptacles (since 1987)
        Ø all receptacles in crawl spaces and unfinished basements (since 1990).

Seismograph

ð A seismograph measures the intensity of earthquake waves using a magnet and a coil of wire

ð One of them is fixed to the case and the other is inertial (suspended by a spring)

ð The relative motion of the magnet and the coil when the Earth shakes induces an emf output

Microphone

ð A coil is connected to a membrane and suspended close to a small permanent
magnet.

ð When sound waves strike the membrane motion of the coil is produced.

ð This motion induces an emf.

ð The frequency of the induced emf will be that of the impinging sound waves.

ð This emf signal is then amplified.