electricity

• what is current?

  flow of electrical charge - A
• what is potential difference?

  driving force that pushes charge round - V
• what is resistance?

  anything that slows down charge flow - ohm
• what does current in a circuit depend on?

  • components resistance - greater resistance, smaller current
  • potential difference across component - greater potential difference, larger current
• what is the size of the current equal?

  rate of flow of charge
• what happens to the current of an ohmic conductor at a constant temperature?

  current is directly proportional to potential difference so resistance doesn't change
• what type of graph is an ohmic conductor?

  linear
• what is an example of an ohmic conductor?

  resistor
• what happens to the current in a filament lamp?

  current increases so temperature increases so resistance increases
• what happens to the current in a diode?

  high resistance in one direction so current only flows in other direction
• what type of graphs are filament lamps and diodes?

  non linear
• what does ldr have a low resistance in?

  brighter light
• what is ldrs used in?

  automatic night lights
• what does thermistors depend on?

  temperature
• what does thermistor have a lower resistance in?

  hotter temperature
• what are thermistors used in?

  thermostats
• what are 3 characteristics of series circuits?

  • current is same
  • total source potential difference is shared between components
  • total resistance of components = sum of resistance
• heat are 2 characteristics of parallel circuits?

  • total current flowing around a circuit = sum of currents through each branch
  • potential difference across each branch is same as source potential difference
• what happens if you add a resistor to a series / parallel circuit?

  • series = increases
  • parallel = decreases
• what is alternating current?

  current that constantly changes direction and produced by an alternating potenti difference
• what is alternating current used in?

  mains supply
• what is direct current?

  current that always flows in same direction and is produced by a direct potential difference
• what is direct current supplied by?

  batteries
• what are 2 facts about uk mains supply?

  • frequency = 50hz
  • potent difference = 230v
• what are 3 facts about the live wire in a three core cables?

  • colour = brown
  • potential difference = 230
  • use = provides alternating potential difference from mains supply
• what are the 3 wire in a 3 core cables?

  • live
  • neutral
  • earth
• what are 3 facts about the neutral wire in a 3 core cables?

  • colour = blue
  • potential difference = around 0
  • use = completes circuit
• what are 3 facts about the earth wire in a 3 core cables?

  • colour = green / yellow
  • potential difference = 0
  • use = stops appliance casing becoming live
• how do electric shocks work?

  1. a person (0v) touches a live wire (230v)
  2. large potential difference produced across body
  3. current flows through body
• when charge flow happens, what else is done?

  work as energy is transferred
• what factors affect the amount of energy an appliance?

  • appliances power
  • how long appliance is on for
• what is power?

  energy transferred per second
• what is a power rating?

  maximum safe power an appliance can operate at
• what is the national grid?

  a system of cables / transformers that connect power stations to consumers
• what does the step down transformer do?

  • decrease potential difference
  • increase current
• what does the step up transformer do?

  • increase potential difference
  • decrease current
• how is static electricity produced?

  1. rub two insulating materials together
  2. electrons move from one to other
  3. both materials become electrically charged. charge on each material is equal and opposite
  4. if an acetate rod and cloth = rod - gains electrons so is negatively charged, cloth - loses electrons so is postively charged
• what is an electric spark?

  passage of electrons across a gap between a charged object and earth
• how is an electric spark produced?

  1. electric charge builds on an object
  2. potential difference between object and earth increases
  3. when potential difference is large enough, there is a spark
• what is an electric field?

  a region in which another charged objects feels a force