Circuit Devices

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Diode

  • Made from a semi-conducting material such as silicon
  • regulates potential difference in circuits
  • lets current flow freely in one direction but not the other (high resistance in the other direction)
  • are really useful in electronic circuit

(http://cdn.physorg.com/newman/gfx/news/2005/diod_symbol.jpg)

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Light Emitting Diodes (LEDs)

  • they emit light when the current flows through it in the forward direction
  • they are being used more as lighting because they use a much smaller current than other forms of lighting
  • they show the presence of a current in the circuit, are often used in appliances to show that they are on
  • Uses: DIGITAL CLOCKS, in TRAFFIC LIGHTS and in REMOTE CONTROLS

(http://upload.wikimedia.org/wikipedia/commons/6/60/Diod_LED_symbol.png)

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Light-dependent resistor (LDR)

  • it is dependent on the intensity of the light
  • in bright light the residtance falls
  • in darkness the resistance is highest
  • Uses: AUTOMATIC NIGHT LIGHTS, OUTDOOR LIGHTING and BURGLAR DETECTORS

(http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect18_.gif)

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Thermistor

  • it is a temperature dependent resistor
  • in hot conditions the resistance drops
  •  in cool conditions the resistance increases
  • Uses: TEMPERATURE DETECTORS, CAR ENGINE TEMPERTURE DETECTORS and ELECTRONIC THERMOSTATS

 (http://t3.gstatic.com/images?q=tbn:ANd9GcSwq1oIe0DqSkU7reACyoPnr1_K0sOkGUOarUjqz2-WZEOF3lM3)

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