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simple phenomena of magnetism

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simple phenomena of magnetism

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Magnetism. Introduction to Magnetism.

IGCSE comittee slide. I obtained this from Physics IGCSE comittee. Thank you for sharing. If the owner find this, kindly email me at fadhilahalias@gmail.com for aknowledgement.

Magnetism. Introduction to Magnetism.

IGCSE comittee slide. I obtained this from Physics IGCSE comittee. Thank you for sharing. If the owner find this, kindly email me at fadhilahalias@gmail.com for aknowledgement.

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simple phenomena of magnetism

  1. 1. PHYSICS – Simple phenomena of magnetism
  2. 2. • fadhilahalias@gmail.com
  3. 3. LEARNING OBJECTIVES Core •Describe the forces between magnets, and between magnets and magnetic materials • Give an account of induced magnetism • Distinguish between magnetic and non- magnetic materials • Describe methods of magnetisation, to include stroking with a magnet, use of d.c. in a coil and hammering in a magnetic field • Draw the pattern of magnetic field lines around a bar magnet • Describe an experiment to identify the pattern of magnetic field lines, including the direction • Distinguish between the magnetic properties of soft iron and steel • Distinguish between the design and use of permanent magnets and electromagnets Supplement Explain that magnetic forces are due to interactions between magnetic fields • Describe methods of demagnetisation, to include hammering, heating and use of a.c. in a coil
  4. 4. Magnets N S Properties Have magnetic fields around them. Attracted? .. or not?
  5. 5. Magnets N S Properties Have magnetic fields around them. Have two opposite poles (N & S) – like poles repel, unlike poles attract. Attracted? .. may be?
  6. 6. Magnets N S Properties Have magnetic fields around them. Have two opposite poles (N & S) – like poles repel, unlike poles attract. Exert little or no force on a non-magnetic material. Attracted? .. possibly?
  7. 7. Magnets N S Properties Have magnetic fields around them. Have two opposite poles (N & S) – like poles repel, unlike poles attract. Exert little or no force on a non-magnetic material.Attract magnetic materials by inducing magnetism in them. N Iron Steel Attracted? .. hopefully?
  8. 8. Magnets N S Properties Have magnetic fields around them. Have two opposite poles (N & S) – like poles repel, unlike poles attract. Exert little or no force on a non-magnetic material.Attract magnetic materials by inducing magnetism in them. N Poles induced in both iron and steel. S N S N Attracted? .. mmmm?
  9. 9. Magnets N S Properties Have magnetic fields around them. Have two opposite poles (N & S) – like poles repel, unlike poles attract. Exert little or no force on a non-magnetic material.Attract magnetic materials by inducing magnetism in them. N Iron loses magnetism – it was only a temporary magnet S N Steel retains magnetism – it became a permanent magnet Attracted? YES!!!
  10. 10. Magnets – make your own! N S S N How strong is it? Not very. Placing a piece of steel near a magnet makes it permanently magnetised, but its magnetism is usually weak.
  11. 11. Magnets – make your own! N How strong is it? Getting stronger. The magnet can be magnetized more strongly by stroking it with one end of a magnet S Wide sweep away from the steel Induced poles
  12. 12. Magnets – make your own! How strong is it? Strongest! The best way of magnetizing is to place the steel bar in a long coil of wire and pass a large, direct (one way) current through the coil. The coil has a magnetic effect which magnetizes the steel. Coil Steel
  13. 13. Magnets – how do they work? N SJust what is happening inside the magnet to make it magnetic?
  14. 14. Magnets – how do they work? N SJust what is happening inside the magnet to make it magnetic? We need to look closely at what is happening to the particles (electrons) inside the magnet.
  15. 15. Magnets – how do they work? N SJust what is happening inside the magnet to make it magnetic? We need to look closely at what is happening to the particles (electrons) inside the magnet. In an unmagnetized material, the tiny electrons, or atomic magnets point in random directions.
  16. 16. Magnets – how do they work? N SJust what is happening inside the magnet to make it magnetic? We need to look closely at what is happening to the particles (electrons) inside the magnet. When the material becomes magnetized, more and more of the tiny atomic magnets line up with each other. They act as one BIG magnet.
  17. 17. Magnets – how do they work? N SJust what is happening inside the magnet to make it magnetic? We need to look closely at what is happening to the particles (electrons) inside the magnet. If a magnet is hit with a hammer, the tiny atomic magnets get thrown out of line again, so the material becomes demagnetised.
  18. 18. Magnets – how do they work? N SJust what is happening inside the magnet to make it magnetic? We need to look closely at what is happening to the particles (electrons) inside the magnet. If a magnet is hit with a hammer, the tiny atomic magnets get thrown out of line again, so the material becomes demagnetised. A magnet will also become demagnetized if heated to high temperature.
  19. 19. Magnetic and non-magnetic
  20. 20. Magnetic and non-magnetic Magnetic material – can be magnetized, and is attracted to magnets. Strongly magnetic materials contain iron, nickel or cobalt (eg. Steel is mainly iron).
  21. 21. Magnetic and non-magnetic Magnetic material – can be magnetized, and is attracted to magnets. Strongly magnetic materials contain iron, nickel or cobalt (eg. Steel is mainly iron). Ferromagnets Hard magnetic materials, eg. Steel, alloys (Alcomax, Magnadur). Difficult to magnetise, but do not lose their magnetism. Used for permanent magnets.
  22. 22. Magnetic and non-magnetic Magnetic material – can be magnetized, and is attracted to magnets. Strongly magnetic materials contain iron, nickel or cobalt (eg. Steel is mainly iron). Ferromagnets Hard magnetic materials, eg. Steel, alloys (Alcomax, Magnadur). Difficult to magnetise, but do not lose their magnetism. Used for permanent magnets. Soft magnetic materials, eg. Iron, Mumetal. Relatively easy to magnetise, but magnetism is temporary. Used in electromagnets and transformers.
  23. 23. Magnetic and non-magnetic Magnetic material – can be magnetized, and is attracted to magnets. Strongly magnetic materials contain iron, nickel or cobalt (eg. Steel is mainly iron). Ferromagnets Hard magnetic materials, eg. Steel, alloys (Alcomax, Magnadur). Difficult to magnetise, but do not lose their magnetism. Used for permanent magnets. Soft magnetic materials, eg. Iron, Mumetal. Relatively easy to magnetise, but magnetism is temporary. Used in electromagnets and transformers. Non-magnetic materials. Metals (brass, copper, zinc, tin and aluminium); non-metals.
  24. 24. Magnetic fields
  25. 25. Magnetic fields Iron filings sprinkled around a magnet Magnetic field lines around the magnet
  26. 26. Magnetic fields Iron filings sprinkled around a magnet Magnetic field lines around the magnet Field lines run from the north pole (N) to the south pole (S). The magnetic field is strongest where the field lines are closer together.
  27. 27. Magnetic fields Using a plotting compass to find the field lines. N S
  28. 28. Magnetic fields Using a plotting compass to find the field lines. N S
  29. 29. Magnetic fields Using a plotting compass to find the field lines. N S
  30. 30. Magnetic fields Using a plotting compass to find the field lines. N S
  31. 31. Magnetic fields Using a plotting compass to find the field lines. N S
  32. 32. Magnetic fields Using a plotting compass to find the field lines. N S
  33. 33. Magnetic fields Using a plotting compass to find the field lines. N S . . . .
  34. 34. Magnetic fields Using a plotting compass to find the field lines. http://www.physbot.co.uk/magnetic-fields-and-induction.html
  35. 35. Magnetic fields Interactions between magentic fields http://www.homofaciens.de/technics-magnetic-field-energy_en_navion.htm When unlike poles are placed near each other, their magnetic fields combine to produce a single field of almost uniform strength.
  36. 36. Magnetic fields Interactions between magentic fields http://www.homofaciens.de/technics-magnetic-field-energy_en_navion.htm When unlike poles are placed near each other, their magnetic fields combine to produce a single field of almost uniform strength. When like poles are placed near each other, their magnetic fields cancel each other, and there is a neutral point where the combined field strength is zero. Neutral point
  37. 37. The Earth’s magnetic field The Earth’s magnetic field is like that around a very large, but very weak, bar magnet.
  38. 38. The Earth’s magnetic field The Earth’s magnetic field is like that around a very large, but very weak, bar magnet. A compass ‘north’ end points north. But a north pole is always attracted to a south pole, so the Earth’s magnetic south pole must actually be in the north.
  39. 39. The Earth’s magnetic field The Earth’s magnetic field is like that around a very large, but very weak, bar magnet. A compass ‘north’ end points north. But a north pole is always attracted to a south pole, so the Earth’s magnetic south pole must actually be in the north. The Earth’s magnetic north is actually over 1200km away from the true geographic north pole.
  40. 40. The Earth’s magnetic field The Earth’s magnetic field is like that around a very large, but very weak, bar magnet. A compass ‘north’ end points north. But a north pole is always attracted to a south pole, so the Earth’s magnetic south pole must actually be in the north. The Earth’s magnetic north is actually over 1200km away from the true geographic north pole. Over a period of time the Earth’s magnetic pole will ‘flip’.
  41. 41. The Earth’s magnetic field The Earth’s magnetic field is like that around a very large, but very weak, bar magnet. A compass ‘north’ end points north. But a north pole is always attracted to a south pole, so the Earth’s magnetic south pole must actually be in the north. The Earth’s magnetic north is actually over 1200km away from the true geographic north pole. Over a period of time the Earth’s magnetic pole will ‘flip’. In the last 10 million years, there have been, on average, 4 or 5 ‘flips’ per million years.
  42. 42. Electromagnets Distinguish between the design and use of permanent magnets and electromagnets
  43. 43. Electromagnets Distinguish between the design and use of permanent magnets and electromagnets Unlike bar magnets, which are permanent magnets, the magnetism of electromagnets can be turned on and off.
  44. 44. Electromagnets Distinguish between the design and use of permanent magnets and electromagnets Unlike bar magnets, which are permanent magnets, the magnetism of electromagnets can be turned on and off. Permanent magnet uses: 1. Needles of compasses. 2. Fridge door seals, holding the doors closed. 3. Loudspeakers and microphones.
  45. 45. Electromagnets Distinguish between the design and use of permanent magnets and electromagnets Unlike bar magnets, which are permanent magnets, the magnetism of electromagnets can be turned on and off. Permanent magnet uses: 1. Needles of compasses. 2. Fridge door seals, holding the doors closed. 3. Loudspeakers and microphones. switch battery coil Soft iron core When a current flows through the coil it produces a magnetic field. This field is temporary and is lost when the current is switched off.
  46. 46. Electromagnets Distinguish between the design and use of permanent magnets and electromagnets Unlike bar magnets, which are permanent magnets, the magnetism of electromagnets can be turned on and off. Permanent magnet uses: 1. Needles of compasses. 2. Fridge door seals, holding the doors closed. 3. Loudspeakers and microphones. switch battery coil Soft iron core When a current flows through the coil it produces a magnetic field. This field is temporary and is lost when the current is switched off. Strength increased by: - Increasing the current - Increasing number of turns
  47. 47. Electromagnets Distinguish between the design and use of permanent magnets and electromagnets Unlike bar magnets, which are permanent magnets, the magnetism of electromagnets can be turned on and off. Permanent magnet uses: 1. Needles of compasses. 2. Fridge door seals, holding the doors closed. 3. Loudspeakers and microphones. switch battery coil Soft iron core When a current flows through the coil it produces a magnetic field. This field is temporary and is lost when the current is switched off. Strength increased by: - Increasing the current - Increasing number of turns Uses: scrapyard electromagnets, circuit breakers, relays, electric bells.
  48. 48. LEARNING OBJECTIVES Core •Describe the forces between magnets, and between magnets and magnetic materials • Give an account of induced magnetism • Distinguish between magnetic and non- magnetic materials • Describe methods of magnetisation, to include stroking with a magnet, use of d.c. in a coil and hammering in a magnetic field • Draw the pattern of magnetic field lines around a bar magnet • Describe an experiment to identify the pattern of magnetic field lines, including the direction • Distinguish between the magnetic properties of soft iron and steel • Distinguish between the design and use of permanent magnets and electromagnets Supplement Explain that magnetic forces are due to interactions between magnetic fields • Describe methods of demagnetisation, to include hammering, heating and use of a.c. in a coil
  49. 49. PHYSICS – Simple phenomena of magnetism

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