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SECTION 6: MAGNETISM AND ELECTROMAGNETISM

SECTION 6: MAGNETISM AND ELECTROMAGNETISM. Chapter 21 Magnetism and Electromagnetism. Magnets attract magnetic materials but not non-magnetic materials. Magnetism is a non-contact force (acts at a distance). Magnetic materials:. iron. steel. nickel. cobalt.

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SECTION 6: MAGNETISM AND ELECTROMAGNETISM

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  1. SECTION 6: MAGNETISM AND ELECTROMAGNETISM Chapter 21 Magnetism and Electromagnetism

  2. Magnets attract magneticmaterials but not non-magnetic materials. Magnetism is a non-contact force (acts at a distance). Magnetic materials: • iron • steel • nickel • cobalt The region around a magnet where a magnetic force can be felt is called the magnetic field. The magnetic field is strongest at the poles of a magnet.

  3. north-seeking pole or north pole south-seeking pole or south pole Unlike poles attract Like poles repel

  4. S N REPULSION S N S S N N ATTRACTION S N N S REPULSION N N S S ATTRACTION

  5. A magnetic field around a bar magnet has a shape and direction. The magnetic field is represented using magnetic field lines (lines of force, flux lines) that show the shape, directionand strengthof the field.

  6. Investigate the shape of the magnetic field between two bar magnets. A B C D N N S S N S N S N S N S N S N

  7. UNIFORM MAGNETIC FIELD. N S Magnetic field lines are parallel and equally spaced apart.

  8. Made from magnetically hard materials, such as steel. Made from magnetically soft materials, such as iron. Retain their magnetism once they have been magnetised. They are easy to magnetise but lose their magnetism easily. Magnetism can be inducedin some materials when they are placed in a magnetic field.

  9. Electromagnetism A wire carrying a current has a magnetic field around it. The magnetic field around a current carrying wire has a circular shape.

  10. The right hand grip rule

  11. The magnetic field around a flat coil

  12. Solenoids The magnetic field around a solenoid has the same shape as the field around a bar magnet. The field inside the solenoid is very strong and uniform. It can be used to magnetise objects.

  13. Polarity of a coil

  14. The strength of the magnetic field around a solenoid can be increased by: • Increasing the current. • Increasing the number of turns on the solenoid. • Using a magnetically soft core such as iron. • Bringing the poles together.

  15. Using electromagnets

  16. The electric bell

  17. Circuit breaker

  18. An electromagnetic door lock There is an iron bar keeping the door locked. If the security officer agrees to let you in, he presses a switch which allows a current to flow through the solenoid. What happens to the iron bar?

  19. The electromagnetic relay

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