1. Explanation of the Reed Switch Motor (RSM) September 2009

2. Since the main switch is open, the is no current in the circuit. Reed Switch Motor in action 0 0

3. The motor begins its rotation clockwise. Since the diode is inversely polarised, it does not light up. The main switch is now closed. Since the magnetic switch is close to a magnet, it too, is closed. Current thus feeds the electromagnet and causes a strong force of repulsion between its north pole and the south pole of the permanent magnet close by. 1 1

4. Since the diode is polarised in the right direction, it lights up for a short time. The diode thus dissipates the energy that would otherwise have caused a spark in the magnetic switch thereby damaging it. The magnetic field of the electromagnet and the force generated decreases rapidly. The main switch is still closed. Since the magnetic switch is far enough away from a magnet, it opens. The current from the source is blocked. Residual current decreases gradually in the loop formed by the electromagnet and the diode. 2 2

5. There is no longer any current in the closed loop formed by the electromagnet and the diode. The electrical energy has completely dissipated. The motor is now turning solely due to the inertia of the rotor. The main switch is still closed. Since the magnetic switch is still far enough away from a magnet, it remains open. Current from the source is still blocked. 3 3

6. 4 4 The source current is therefore still blocked. Since the electromagnet’s core is ferromagnetic, a weak force of attraction appears between it and the approaching magnet. The main switch is still closed. A magnet is getting closer to the magnetic switch. It is not yet close enough, however, so the magnetic switch remains open.

7. 1 1 And so, the same cycle starts again four times for each complete rotation of the rotor.

8. 2 2

9. 3 3

10. 4 4

11. 1 1

12. 2 2

13. 3 3

14. 4 4

15. 1 1

16. 2 2

17. 3 3

18. 4 4

19. 1 1

20. 2 2

21. 3 3

22. 4 4

23. 1 1

24. 2 2

25. 3 3

26. 4 4

27. 1 1

28. 2 2

29. 3 3

30. 4 4

31. 1 1

32. 2 2

33. 3 3

34. 4 4

35. 1 1

36. 2 2

37. 3 3

38. 4 4