electricity

• What are the two coils of wire in a transformer called?


  Primary and secondary coils.
• Why are the coils in a transformer wrapped around the iron core?


  Because iron is easily magnetised.
• What happens when current flows through the primary coil?

  It generates a changing magnetic field.
• What happens when the changing magnetic field passes through the secondary coil?

  Induces potential difference.
• What is the only type of current transformers work on?

  Alternating current.
• What type of transformer has more turns in the secondary coil than the primary coil?


  Step-up transformer.
• What does a step up transformer do?


  Increases potential difference and decreases current.
• Where does electric current flow?

  From the negative end to the positive end.
• For components connected in parallel the potential difference of each component is the same.
• What is a battery?

  Two or more cells connected together.
• Current moving through a resistor is directly proportional to the potential difference.
• Resistance will only stay constant if the temperature is constant.
• The current through a filament lamp is not directly proportional to the potential difference.
• Why is the current through a filament lamp not directly proportional to the potential difference?

  Because the filament gets hot increasing the resistance.
• What happens to the atoms in a filament at high temperatures?

  They vibrate more causing electrons in the current to collide more with the atoms so more energy is needed to push the current through the filament.
• Is the filament lamp an ohmic conductor?

  No.
• Where does the current flow in a diode?

  In one direction only.
• Why does the current in a diode only flow in one direction?

  A diode has a very high resistance in the other direction.
• Diodes are extremely useful for controlling the flow of current in circuits.
• Where can light emitting diodes be found?

  1. Flash on a camera.
  2. LED lightbulbs.
  3. LED televisions.
• What's the difference between a normal diode and a light emitting diode?

  A LED gives off light when a current flows through and a normal diode doesn't.
• LED's are an extremely energy efficient source of light.
• Resistors in series add together.
• The total resistance of two resistors in parallel is less than the resistance of the smallest individual resistor.
• In dark conditions the light dependent resistor has a high resistance.
• In the light the light dependent resistor has low resistance.
• LDR's can be used in garden lamps.
• The resistance of a thermistor decreases if the temperature increases.
• What is power?


  The rate at which energy is transfered.
• What is power measured in?

  Watts.
• What is a direct current?

  Flow of electric charge in one direction.
• What is alternating current?


  Current which constantly changes direction.
• What is an advantage of using alternating current?

  Very easy to use a transformer to increase or decrease potential difference.
• What is the alternating current in the uk?

  50 hertz
• What is the potential difference of alternating current in the uk?

  230V.
• Why are wires made out of copper?

  Copper is a good conductor of elecricity.
• what are the coatings of the wire made out of?

  Plastic which doesn't conduct electricity.
• What is the role of the brown wire? (live wire)

  Carries the alternating potential difference from the supply.
• What is the live wire connected to?

  A fuse in the plug.
• What is the role of the blue wire? (neutral wire)


  Completes the circuit and has a potential difference of 0v.