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UNIT 13: RELAYS AND SWITCHES INTRODUCTION Relays and switches are electromechanical devices that open or close circuits. A relay uses a coil to move contacts electrically. Switches are operated manually by a person. STORY 1: Electromagnetic Relays A relay consists of a coil, an iron core, and one or more sets of contacts. When current flows through the coil, it creates a magnetic field that pulls a movable armature. This changes the contact position. Relays can switch high voltage or current us