Topic: Magnetism and Electromagnetism

6.04 understand the term magnetic field line

Around every magnet there is a region of space where we can detect magnetism (where magnetic materials will be affected).

This is called the magnetic field and in a diagram we represent this with magnetic field lines. 

The magnetic field lines should always point from north to south.

6.05 know that magnetism is induced in some materials when they are placed in a magnetic field

When magnetic materials are bought near or touch the pole of a strong or permanent magnet, they become magnets. This magnetic character is induced in the objects and it is removed when the permanent magnet is removed. This is a temporary magnet

Magnetism is induced in the paperclips so each paperclip can attract another one

6.06 practical: investigate the magnetic field pattern for a permanent bar magnet and between two bar magnets

  1. Place your bar magnet in the centre of the next page and draw around it.
  2. Place a compass at one pole of the bar magnet.
  3. Draw a ‘dot’ to show there the compass is pointing,
  4. Move the compass so the opposite end of the needle is pointing to the dot,
  5. Repeat steps 3 and 4 until to reach the other pole of the magnet.
  6. Do this procedure at least 5 times from different points on the pole of the magnet.
    *Tip, try to be as accurate as possible when drawing your dots*
  7. Join up your dots to create the field line plots

6.11 know that there is a force on a charged particle when it moves in a magnetic field as long as its motion is not parallel to the field

The movement of the charged particle is a current so it produces a magnetic field. This magnetic field interacts with the permanent magnetic field to create a force. The force is perpendicular to the direction of motion and the permanent magnetic field.

6.12 understand why a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers

Motor

  • Current flows in the wire/coil.
  • This creates a magnetic field around the wire/coil.
  • This magnetic field interacts with the field from the permanent magnet.
  • This produces a force on the wire/coil which moves the wire/coil.
  • The split-ring commutator changes the direction of the current every half turn as it spins. This reverses the direction of the forces, allowing the coil to continue spinning.

Loudspeaker

  • An alternating current from the source passes though the coils in the speaker.
  • This current is constantly changing direction and magnitude
  • This current creates a magnetic field around the coil
  • This field interacts with the magnetic field from the permanent magnets
  • Creating a constantly changing force on the coil.
  • This causes the coil to vibrate in and out as the direction of the force changes, moving the cone
  • The cone causes vibrations which we hear as sound waves.

6.14 describe how the force on a current-carrying conductor in a magnetic field changes with the magnitude and direction of the field and current

If you increase the magnitude of the current through a wire or the size of the magnet being used, you increase the force on the wire.

If you change the direction of the current or reverse the poles of the magnet, you change the direction of the force on the wire

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Section 1: Principles of chemistry

      a) States of matter

      b) Atoms

      c) Atomic structure

     d) Relative formula masses and molar volumes of gases

     e) Chemical formulae and chemical equations

     f) Ionic compounds

     g) Covalent substances

     h) Metallic crystals

     i) Electrolysis

 Section 2: Chemistry of the elements

     a) The Periodic Table

     b) Group 1 elements: lithium, sodium and potassium

     c) Group 7 elements: chlorine, bromine and iodine

     d) Oxygen and oxides

     e) Hydrogen and water

     f) Reactivity series

     g) Tests for ions and gases

Section 3: Organic chemistry

     a) Introduction

     b) Alkanes

     c) Alkenes

     d) Ethanol

Section 4: Physical chemistry

     a) Acids, alkalis and salts

     b) Energetics

     c) Rates of reaction

     d) Equilibria

Section 5: Chemistry in industry

     a) Extraction and uses of metals

     b) Crude oil

     c) Synthetic polymers

     d) The industrial manufacture of chemicals