PhysicsChapter 9: Electronics
Relay
Introduction
A relay is an electrically operated switch. In a traditional electromagnetic relay, current through a coil produces a magnetic field. This magnetic effect moves an armature and changes electrical contacts. A relay therefore allows one electrical circuit to control the switching of another circuit.
Definition
Main Parts
A basic electromagnetic relay contains: * coil/electromagnet; * armature; * contacts; * spring or return mechanism.
Why Relays Are Useful
A relatively small control current can operate contacts controlling another circuit. The control circuit and switched circuit can also be electrically isolated in many relay arrangements.
Applications
Relays are used in: * automatic control systems; * alarms; switching circuits; protection/control equipment.
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Relay
Sticky Notes · Quick Revision
RELAY
- Current in coil
- ↓
- Magnetic field
- ↓
- Armature moves
- ↓
- Contacts switch
60-second revision
- Relay → electrically operated switch.
- Coil → magnetic field.
- Armature → moves.
- Contacts → open/close circuit.
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