Electricity

• Circuit symbols

  Used to draw circuits simply
• Circuit components

  • Power supply (cell)
  • Ammeter
  • Lamp
  • Voltmeter
  • Resistor
  • Lamp
  • Diode
  • Light dependent resistor
  • Thermistor
• Ammeter


  Measures current, connected in series
• Voltmeter


  Measures potential difference, connected in parallel
• Electric current


  Rate of flow of electric charge
• Ohmic conductors


  • Current proportional to potential difference
  • Resistance constant
• Filament lamp


  • Resistance increases as it gets hotter and gives out more light
• Diode


  • One-way valve, allows current to flow in one direction only
• Light dependent resistor (LDR)


  • Resistance decreases as light intensity increases
• Thermistor


  • Resistance decreases as temperature increases
• Series circuit


  Components connected one after another, same current in each component
• Parallel circuit


  Separate loops, different current in each component, same potential difference across each component
• Alternating current (AC)


  Current flows back and forth, used in household mains
• Mains supply


  230V, 50Hz frequency in UK
• Mains cable


  Brown wire - live, Blue wire - neutral, Green/yellow wire - earth
• unit: V

  amount of energy transferred per unit of charge


  what is meant by potential difference in a circuit and unit?
• Limits the flow of current in a circuit ohms

  fixed resistor
• the rate of flow of electric charge/electrons

  charge C (coulombs) =current A (amps) x time s(seconds)


  state an equation that links current, charge and time, with units for each
• National Grid


  System of cables and transformers linking power stations to consumers
• the rate of flow of electric charge

  current
• divide by 1000


  Milliamps to amps
• Transformer


  Primary and secondary coils wrapped around iron core, allows voltage to be stepped up or down
• fixed: constant resistor

  variable: can change resistance


  difference between fixed and variable resistor
• greater the resistance


  longer the length of the wire
• how does a fixed resistor work
• Static electricity


  Caused by transfer of electrons between insulators, can create attractive or repulsive forces
• fixed resistor


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• variable resistor (works with slider thing)


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• Ammeter


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• Electric field


  Region around a charged object where other charges experience a force
• voltmeter


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• Diode


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• LDR


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• Thermistor


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• motor


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• converts electrical energy into mechanical energy

  motor
• cell


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• battery


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• switch (open)


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• filament lamp


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