electricity

• Electrical current

  The flow of electrical charge - it will only flow around a closed circuit if there is a potential difference
• Potential difference

  The driving force that pushes the charge around
• Resistance

  Anything that slows the flow down
• Greater the resistance across a component


  Smaller the current that flows (for a given potential difference across the component)
• LDR


  • A resistor dependent on the intensity of light - brighter the light, lower the resistance and vice versa
• Thermistor


  • A temperature dependent resistor - in hot conditions, the resistance drops
• Series circuit

  1. All components are connected end to end

  2. If one component is disconnected/broken everything stops

  3. Potential difference is shared (Vtotal = V1 + V2)

  4. Current is the same (I1 = I2)

  5. Resistance adds up (Rtotal = R1 + R2)
• Parallel circuits

  1. If you remove or disconnect a component it won't affect the rest

  2. Potential difference is the same (V1 = V2)

  3. Current is shared (Itotal = I1 + I2)

  4. Adding a resistor in parallel reduces the total resistance
• AC


  Alternating current when the current is constantly changing direction
• DC


  Direct current when the current is flowing in the same direction
• Cables have three separate wires


  • Live wire (brown) provides alternating potential difference
  • Neutral wire (blue) completes the circuit
  • Earth wire (yellow and green) - protects the wiring and carries no current
• The national grid is a giant web of wires that covers the whole of Britain, transporting electricity from power stations to homes everywhere
• The national grid has to use a high potential difference and a low current


  • You need a high pd or current to transmit loads of power
  • A high current loses lots of energy through heat
  • Its cheaper to boost the pd
• Transformer

  Has a primary coil and a secondary coil, used to change potential difference
• Static electricity

  All about charges which are not free to move
• Static electricity

  1. When certain insulating materials are rubbed together negatively charged electrons will be scraped off one and dumped on the other

  2. This will leave all material electrically charged with a positive static charge on one and an equal negative charge on the other
• Electrical field

  Created around any electrically charged object, the closer to an object you get the stronger the field is
• A charged object is placed in the electrical field of another object


  It feels a force, causing an attraction/repulsion
• Sparks are caused when there is a high enough pd between a charged object and the earth
• High potential differences cause a strong electric field between the charged object and the earthed object
• The strong electric field causes electrons in the air particles to be removed