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Switches, Fuses and Relays

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Schematic Symbols for Switches and Fuses

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Switches

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Cutaway View of a SPDT Toggle Switch

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Standard Switch vs Three Way Switch

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Three Way Switch Connection

SPDT SPST

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Fuses and Circuit Breakers

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Three Wire Grounded Systems

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Grounding in Electrical Systems

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Wire Gauge

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Electromagnetism and Electromagnetic Fields

Electromagnetism is the

production of a magnetic field by

current in a conductor Electromagnets are used in

devices such as tape recorders,

electric motors, speakers,

solenoids, and relays

When current passes through a

conductor, an electromagnetic

field is created around the

conductor

Magnetic field is stronger

close to the conductor

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Direction of Lines of Force

The direction of the lines of force surrounding a conductor

depend upon the direction of current flow

The left-hand rule is used to determine the direction of the

lines of force (for electron flow)

If the conductor is grasped in the left hand, with the thumb

pointing in the direction of electron current flow, the fingers of

the left hand point in the direction of the magnetic lines offorce

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Magnetic Switch in Burglar Alarm

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Operation of a Magnetic Switch

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Solenoid

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Operation of a Solenoid

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Relay

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SPDT Relay

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Reed Relay