1. Topic 1 : Magnetic Concept and Transformer
Magnetism
Magnetic Circuit
Transformer Construction
Transformer equivalent circuit
Transformer test, efficiency and regulation.

2. MAGNETISM

3. Magnetic field A magnet has two poles – N and S
Shape of steel fillings on a sheet over a magnet are shown below.

4. Magnetic field
The shape and density of the chains formed enable us to form a mental picture of a magnetic field and lead to the idea of magnetic flux lines.
The density of the lines depends on the strength of the magnet.
The area in which the steel filling are affected by the magnet is become thinner further away from the magnet.

5. Characteristic of magnetic flux
The direction of flux is from North to South.
Each line of magnetic flux forms a closed loop.
Lines of electric flux never intersect.
Lines of magnetic flux are like stretched elastic cords, always trying to shorten themselves.
Lines of magnetic flux which are parallel and in the same direction repel one another.

6. Magnetic field of a current carrying conductor
Current going in (left)
Current coming out (right).
Solenoid.

7. Force on current carrying conductor
Flux of magnet and conductor
Interaction of flux produces force S N
Force S N

8. Force on current carrying conductor
Left-hand rule
Index finger
FLUX
Thumb
FORCE
Middle finger
CURRENT

9. Electromagnetic induction
Two experiments performed by Michael Faraday.
Electric current could be produced by the movement of magnetic flux relative to the coil.

10. Electromagnetic induction
Direction of induced emf.
Fleming’s right-hand rule.
Lenz’s law - The direction of an induced emf is always such that it tends to set up a current opposing the motion or the change of flux responsible for inducing that emf.
Thumb
FORCE
Middle finger
CURRENT
Index finger
FLUKS

11. MAGNETIC CIRCUIT

12. Basic Definitions

13. Basic Definitions

14. Basic Definitions

15. Basic Definitions

16. Basic Definitions Permeability of different materials
Notice the nonlinearity

17. Basic Definitions

18. Basic Definitions

19. Comparison of electric and magnetic circuit
Electric circuit
Magnetic circuit
EMF, v
MMF, NI
Electric field strength, v/m
Magnetic field strength, H
Current, I
Flux, Φ
Current density, I/A
Flux density, B

20. Comparison of electric and magnetic circuit
Since the magnetic circuit behaves in similar ways as an electric circuit, the laws of electric circuit are applicable to the magnetic circuit.
Ohm’s law equivalent :
F = ΦS.
Kirchoff law equivalent:
Φin = Φout
Total NI = Total Hl
A magnetic circuit can be redrawn as electric circuit equivalent to facilitate the analysis.

21. Comparison of electric and magnetic circuit