1. ECE 201 Circuit Theory I1 Electromagnetic Devices

2. ECE 201 Circuit Theory I2 Solenoid Has a movable iron core called a plunger

3. ECE 201 Circuit Theory I3

4. 4 Unenergized state Plunger is extended

5. ECE 201 Circuit Theory I5 Plunger is extended by the force of the spring

6. ECE 201 Circuit Theory I6 Energized State Plunger is retracted

7. ECE 201 Circuit Theory I7 Both iron cores become magnetized, and the South pole of the stationary core attracts the North pole of the movable core, causing it to slide inward, retracting the plunger and compressing the spring. This happens as long as there is sufficient current. When the current is turned off, the magnetic fields collapse and the force of the spring pushes the plunger out.

8. ECE 201 Circuit Theory I8 Uses of Solenoids Provide movement –Door locks –Valves

9. ECE 201 Circuit Theory I9 Relays Used to open or close contacts (switches) Mechanical Relay

10. ECE 201 Circuit Theory I10

11. ECE 201 Circuit Theory I11 Terminal Identifications 1 – Common (COM)2 – Normally Closed (NC)3 – Normally Open (NO) 4 and 5 – Coil This is a single – pole double – throw relay

12. ECE 201 Circuit Theory I12 Unenergized State Normally Closed Continuity between terminals 1 and 2 Armature is held against the upper contact by the force of the spring

13. ECE 201 Circuit Theory I13 Energized State Normally Closed contact is opened, Normally Open contact is closed.

14. ECE 201 Circuit Theory I14

15. ECE 201 Circuit Theory I15 Energized State Continuity between terminals 1 and 3 Armature is pulled down by the electromagnetic field

16. ECE 201 Circuit Theory I16 Typical Construction and Circuit Symbol

17. ECE 201 Circuit Theory I17 Loudspeaker Interaction between the fields of a coil and a permanent magnet

18. ECE 201 Circuit Theory I18 South pole of permanent magnet is positioned within the coil

19. ECE 201 Circuit Theory I19 Magnetic field produced by the current interacts with the permanent magnet field, causing the coil to move right

20. ECE 201 Circuit Theory I20 When the current in the coil reverses, its field is in the opposite direction, causing the coil to move left.

21. ECE 201 Circuit Theory I21 For a time – Varying Signal

22. ECE 201 Circuit Theory I22 Coil motion in both directions Time – Varying signal (voltage or current)