1. Electro-Magnetism
© D Hoult 2008

2. Magnetic Field Shapes

3. Magnetic fields are represented by lines called lines of magnetic force or lines of magnetic flux

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

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

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

7. Field due to a straight current-carrying conductor

8. Field due to a straight current-carrying conductor

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

10. To remember the sense of the magnetic field, think about

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

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

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

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

15. Field due to a short current-carrying coil of wire

16. Field due to a short current-carrying coil of wire

17. Field due to a short current-carrying coil of wire

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

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

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

21. This field is similar to that of a bar magnet

22. This field is similar to that of a bar magnet

23. This field is similar to that of a bar magnet

24. This field is similar to that of a bar magnet

25. Current into plane of diagram

26. Current into plane of diagram
Current out of plane of diagram

27. Fields due to two parallel current-carrying conductors

28. Fields due to two parallel current-carrying conductors
Currents flowing in the same sense

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

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

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

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

33. Fields due to two parallel current-carrying conductors
Currents flowing in the same sense
The two conductors attract each other

34. Currents flowing in opposite sense

35. Close to the conductors the field is very nearly circular

37. The field is similar in shape to the field of a

38. The field is similar in shape to the field of a short coil

39. The field is similar in shape to the field of a short coil
The two conductors repel each other