1. Electro-Magnetism © David Hoult 2009

2. Magnetic Field Shapes © David Hoult 2009

3. Magnetic fields are represented by lines called lines of magnetic force or lines of magnetic flux © David Hoult 2009

4. Magnetic fields are represented by lines called lines of magnetic force or lines of magnetic flux These lines show the direction of the force which would act on a free north magnetic pole placed in the field © David Hoult 2009

5. Magnetic fields are represented by lines called lines of magnetic force or lines of magnetic flux These lines show the direction of the force which would act on a free north magnetic pole placed in the field However, since free north magnetic poles don’t exist... think of the lines as showing which way a very small compass would point if placed in the field © David Hoult 2009

6. Magnetic fields are represented by lines called lines of magnetic force or lines of magnetic flux These lines show the direction of the force which would act on a free north magnetic pole placed in the field However, since free north magnetic poles don’t exist... think of the lines as showing which way a very small compass would point if placed n the field The “density” of lines on a diagram indicates the strength of the magnetic field © David Hoult 2009

7. Field due to a straight current-carrying conductor © David Hoult 2009

8. Field due to a straight current-carrying conductor © David Hoult 2009

9. It is found that a compass always points perpendicular to the conductor so we conclude that the lines form circles (or cylinders) round the conductor © David Hoult 2009

10. To remember the sense of the magnetic field, think about © David Hoult 2009

11. To remember the sense of the magnetic field, think about opening a bottle of wine. © David Hoult 2009

12. To remember the sense of the magnetic field, think about opening a bottle of wine. © David Hoult 2009

13. To remember the sense of the magnetic field, think about opening a bottle of wine. demo... © David Hoult 2009

14. To remember the sense of the magnetic field, think about opening a bottle of wine. © David Hoult 2009

15. Field due to a short current-carrying coil of wire © David Hoult 2009

16. Field due to a short current-carrying coil of wire © David Hoult 2009

17. Field due to a short current-carrying coil of wire © David Hoult 2009

18. Field due to a long current-carrying coil of wire (also called a solenoid) © David Hoult 2009

19. Field due to a long current-carrying coil of wire (also called a solenoid) © David Hoult 2009

20. Field due to a long current-carrying coil of wire (also called a solenoid) © David Hoult 2009

21. This field is similar to that of a bar magnet © David Hoult 2009

22. This field is similar to that of a bar magnet © David Hoult 2009

23. This field is similar to that of a bar magnet © David Hoult 2009

24. This field is similar to that of a bar magnet © David Hoult 2009

25. This field is similar to that of a bar magnet © David Hoult 2009

26. Current into plane of diagram © David Hoult 2009

27. Current into plane of diagram Current out of plane of diagram © David Hoult 2009

28. Fields due to two parallel current-carrying conductors © David Hoult 2009

29. Fields due to two parallel current-carrying conductors Currents flowing in the same sense © David Hoult 2009

30. Fields due to two parallel current-carrying conductors Currents flowing in the same sense © David Hoult 2009

31. Fields due to two parallel current-carrying conductors Currents flowing in the same sense © David Hoult 2009

32. Fields due to two parallel current-carrying conductors Currents flowing in the same sense © David Hoult 2009

33. Fields due to two parallel current-carrying conductors Currents flowing in the same sense © David Hoult 2009

34. Fields due to two parallel current-carrying conductors Currents flowing in the same sense The two conductors attract each other © David Hoult 2009

35. Currents flowing in opposite sense © David Hoult 2009

36. Close to the conductors the field is very nearly circular © David Hoult 2009

38. The field is similar in shape to the field of a © David Hoult 2009

39. The field is similar in shape to the field of a short coil © David Hoult 2009

40. The field is similar in shape to the field of a short coil The two conductors repel each other © David Hoult 2009