What colour LED lamp is commonly used for domestic use?

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RRB ALP CBT 2 Electronic Mechanic Previous Paper: Held on 23 Jan 2019 Shift 1
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  1. White
  2. Black
  3. Red
  4. Green

Answer (Detailed Solution Below)

Option 1 : White
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Detailed Solution

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Light Emitting Diode:

  • A light-emitting diode (LED) is a semiconductor light source.
  • Electroluminescence is the working principle of LED.
  • A light-emitting diode emits light when a current flows through it.
  • Infrared LEDs are used in remote-control circuits.
  • Warm white lighting fixtures are often preferred in living rooms to create a peaceful atmosphere.
  • The warm white lights are a good choice to compliment earthy tones and wood furniture.
  • White light is obtained by using multiple semiconductors or a layer of light-emitting phosphor on the semiconductor device.

Important Points

SSC JE Electrical 63 20Q Basic Electronics Hindi.docx 5

  • A light-emitting diode (LED) is a semiconductor device that emits visible light when an electric current passes through it
  • Light Emitting Diode (LED) works only in the forward bias condition
  • When free electrons reach the junction or depletion region, some of the free electrons recombine with the holes in the positive ions
  • Free electrons recombine with holes in the depletion region
  • In a similar way, holes from the p-side recombine with electrons in the depletion region. 
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