EET

• Atom


  The smallest part of an element that can take part in a chemical change
• Molecule


  A group of atoms bonded together
• Nucleus


  The positively charged central core of an atom made up of protons and neutrons
• Proton


  A stable sub-atomic particle occurring in all atoms with a positive charge
• Neutron


  A stable sub-atomic particle with no charge
• Electron


  A stable sub-atomic particle with a negative charge
• Ions


  Atoms or molecules that have gained or lost electrons
• Conductor


  A material that conducts electricity
• Insulator


  A material that doesn't readily conduct electricity
• Semi-conductor


  A material that can conduct electricity under certain conditions
• Static electricity


  A build-up of charge on the surface of an object
• When extra electrons enter an object, the object becomes negatively charged
• When electrons leave an object, the object becomes positively charged
• Opposite charges attract each other
• Similar charges repel each other
• Terminologies relating to electrical measurement and quantities

  • Current
  • Charge
  • Potential difference
  • Electromotive force (e.m.f.)
• Current


  The flow of electrons, or the flow of charge. The rate of this flow of charge is measured in amperes
• Charge


  The quantity of electricity. One coulomb of charge is conveyed in one second by a current of one amp
• Potential difference


  One volt is the energy transferred by one coulomb as it passes between two points in a circuit
• Electromotive force (e.m.f.)


  The voltage produced by a source of electricity
• Static electricity causes this. It is a type of induced charge.
• Terminologies relating to electrical measurement and quantities

  • Current
  • Charge
  • Potential difference
  • Electromotive force (e.m.f.)
  • Power
  • Energy
  • Resistance
  • Capacitance
  • Inductance
  • Frequency
• Electromotive force (e.m.f.)


  The voltage produced by an electrical power source, e.g. an e.m.f. of 9 V for a battery or an e.m.f. of 115 V for a mains supply
• Power


  The rate at which energy is transferred by electrically powered items, e.g. a light bulb may be 60 W, a fridge may be 200 W
• Energy


  This is the ability to perform work or to move or change things
• Resistance


  The level of opposition to the flow of current in a circuit
• Capacitance


  The ability to store electric charge
• Inductance


  The opposition created by a changing current in a magnetic field which induces a reverse voltage
• Frequency


  The rate at which alternating current (a.c.) completes a cycle
• Current in circuits


  1. Electrical charges move round circuits made up of metal wires and components

  2. Current is not lost or used up as it travels around the circuit, but is transformed to power electrical devices

  3. A small amount of energy is lost as heat
• Conventional current is described in terms of a flow of positive charge. In circuits the energy is actually carried by a flow of negative charge. This means that the particles carrying charge are moving in the opposite direction to the conventional current.
• The main sources of an electromotive force

  • Chemical (e.g. battery)
  • Thermal (heating or lighting)
  • Magnetic
• Potential difference


  The cause of the movement of charge. A charged particle will move to a position where it will have less potential energy and so will move to a lower point in an electric field.
• The effects of electricity

  • Chemical effect
  • Thermal (heating/lighting) effect
  • Magnetic effect
• Electromotive force (e.m.f.)


  The total force measured in volts causing a potential difference between two points, thus causing a flow of electrons.
• A current cannot exist without a potential difference.
• The bigger the difference, the bigger the flow. So a 115 V mains supply has a greater flow than a 9 V cell battery.
• Magnets


  • Attraction or repulsion of one material by another material
  • Materials that are attracted by a magnet such as iron, steel, nickel and cobalt have the ability to become magnetised
• Magnetic field


  A region of space in which a magnetic material will experience a force
• Types of magnets


  • Permanent magnet
  • Electromagnet