Electromagnetic relay

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• Electromagnetic relay

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Description

• Electrically controlled switch
• Current through coil
• Magnetises soft iron core
• Soft iron armature moves
• Contacts join

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Normally Open NO Relay

• No current flowing through the coil
• Contacts are not made
• Coil must be energised for switched circuit to
  work

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Normally Closed NC Relay

• No current flowing through the coil
• Contacts are made
• Coil must be energised for switched circuit to
  stop working

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In a circuit

• Low current flows through coil
• Attracts armature
• Switched circuit connected
• Lamp lights
• BUT Coil is an inductive load
• Add protection diode
• Prevent high voltage spike

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