TOPIC OF ELECTROMAGNETISM.PHYSICS NOTES FORM 4
- 2. Electromagnetism This is the type of a magnet that is made from electricity. There is a relationship between electricity and magnetism. Note; current carrying conductor has magnetism around it.
- 3. Rules in Electromagnets To determine the current or field lines directions, use; a. Maxwell’s cork screw rule b. Right hand grip rule.
- 4. a. Maxwell’s cork screw rule The direction of the screw indicate direction of current while the direction of force of the thumb is the field lines of force
- 5. a. Maxwell’s cork screw rule
- 6. b. Right hand grip rule The direction of the thumb indicate the current direction while the rest of the fingers points at the direction of the magnetic field.
- 7. b. Right hand grip rule
- 8. Fleming's Left Hand Rule The thumb indication direction of force, first finger indicates magnetic field lines force and the second finger indicates current direction.
- 9. Fleming's Left Hand Rule
- 10. Current Conductor The current carrying conductor has magnetic field around it. This makes it experiences some force when it passes through magnets.
- 11. Current Conductor To determine the direction of force, Flemings left hand rule is applied. Next slide explains how this rule is applied.
- 12. Fleming Left Hand Rule a. Determine current direction in the following diagrams;
- 13. Fleming Left Hand Rule a. Determine direction of force in the following diagrams;
- 14. Fleming Left Hand Rule a. Determine magnetic poles in the following diagrams;
- 15. Electromagnetic Induction If current carrying conductor cuts magnetic field e.m.f is produced. The principal is known as electromagnetic induction.
- 17. Electromagnetic Induction The amount of e.m.f depends on; 1. Strength of magnet 2. Number of turns 3. Rate/speed
- 18. Laws of Electromagnetic Induction The Laws of Electromagnetic Induction are; 1. Faraday’s law 2. Lenz’s law
- 19. 1. Faraday’s law This states that the magnitude of the induced e.m.f in a conductor is directly proportional to speed of motion a magnet.
- 20. 2.Lenz’s law This states that the induced e.m.f is always acts to opposite to the cause. This means that induced current flows in direction such that opposes the change producing it.
- 21. Uses Electromagnets Electromagnets are used in; 1. Electric motor 2. Loud speaker 3. Generator
- 23. 1. Electric motor If the switch I closed, current flows through the coil and produces magnetic field. The magnetic field in the coil and that of permanent magnet interact.
- 24. 1. Electric motor The interaction causes push on the left hand side of the coil. The coil rotates in a clockwise direction and its momentum carries it forward.
- 25. 1. Electric motor The motor keeps on rotating hence the motor effect. The rotation can be reversed by reversing current direction .
- 26. 2. Loud speaker
- 27. 2. Loud speaker If electric current is passed through the coil, its magnetic fields interferes with that of magnet.
- 28. 2. Loud speaker This makes paper cone vibrates and sound waves are given out. This is how moving coil loud speaker produces sound
- 29. 3. Generator There are 2 types of generators; a. AC generator b. DC generator
- 30. a. AC Generator
- 31. a. AC Generator This is made up of a coil that rotates around a magnet. The coil rotates around between the poles of magnet.
- 32. a. AC Generator The coil cuts the magnetic field hence inducing e.m.f /current. The ac current is taken to external circuit through brushes.
- 33. a. AC Generator The basic structure of ac generator includes a coil and two slip rings.
- 34. a. DC Generator
- 35. b. AC Generator This is also made up of a coil that rotates around a magnet. The coil rotates around between the poles of magnet.
- 36. b. AC Generator The coil cuts the magnetic field hence inducing e.m.f /current. The dc current is taken to external circuit through brushes.
- 37. b. AC Generator The basic structure of dc generator includes a coil and slip rings are replaced by split ring commutator.
- 39. 4.Moving Coil Microphone This is the moving coil microphone is a device for changing sound energy into electrical energy.
- 40. 4.Moving Coil Microphone It has a diaphragm with alight coil connected to it. The coil is placed in between two poles of magnet of a strong cylindrical .
- 41. 4.Moving Coil Microphone If a person speaks through a microphone, sound energy sets diaphragm into vibrations. This moves the coil back and forth between magnetic poles.
- 42. 4.Moving Coil Microphone The process induces alternating current that is amplified(made larger) in the loud speaker.