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Subelement C
Components
Section 27
Light Emitting Diodes
What type of bias is required for an LED to produce luminescence?
  • Reverse bias.
  • Correct Answer
    Forward bias.
  • Logic 0 (Lo) bias.
  • Logic 1 (Hi) bias.

What type of bias is required for an LED to produce luminescence?

Forward bias

From codygasser:

An LED (Light Emitting Diode) is a unidirectional device, meaning current only flows through it in one direction.

Forward Bias means that the current is flowing through the LED causing it to light up.

If it is reverse biased, the current cannot flow and the LED will not light up.


Please see Electronics Tutorials site for the article The Light Emitting Diode

Also, please see Physics and Radio Electronics site for the article Light Emitting Diode (LED)

And, please see 3 Nd Edu site for the article What is a light-emitting diode?

For additional information, please see PV Education site for the article Bias of PN Junctions, especially paragraph on Diodes under Forward Bias.

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What determines the visible color radiated by an LED junction?
  • The color of a lens in an eyepiece.
  • The amount of voltage across the device.
  • The amount of current through the device.
  • Correct Answer
    The materials used to construct the device.

What determines the visible color radiated by an LED junction?

The materials used to construct the device.

The semiconductor materials used to build the diodes PN junction will affect the frequency of light generated, and these different frequencies result in different light colors. It is the number of photons radiated ending up as different colors.

For additional explanations please see Electronics Hub site for the article Light Emitting Diode Basics

Please see Electronics Tutorials site for the article The Light Emitting Diode

Also, please see Physics and Radio Electronics site for the article Light Emitting Diode (LED)

And, please see 3 Nd Edu site for the article What is a light-emitting diode?

For additional information, please see PV Education site for the article Bias of PN Junctions, especially paragraph on Diodes under Forward Bias.

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What is the approximate operating current of a light-emitting diode?
  • Correct Answer
    20 mA.
  • 5 mA.
  • 10 mA.
  • 400 mA.

What is the approximate operating current of a light-emitting diode?

20 mA.

For additional explanations please see Electronics Hub site for the article Light Emitting Diode Basics

Please see Electronics Tutorials site for the article The Light Emitting Diode

Also, please see Physics and Radio Electronics site for the article Light Emitting Diode (LED)

And, please see 3 Nd Edu site for the article What is a light-emitting diode?

For additional information, please see PV Education site for the article Bias of PN Junctions, especially paragraph on Diodes under Forward Bias.

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What would be the maximum current to safely illuminate a LED?
  • 1 amp.
  • 1 microamp.
  • 500 milliamps.
  • Correct Answer
    20 mA.

What would be the maximum current to safely illuminate a LED?

20 mA.

For additional explanations please see Electronics Hub site for the article Light Emitting Diode Basics

Please see Electronics Tutorials site for the article The Light Emitting Diode

Also, please see Physics and Radio Electronics site for the article Light Emitting Diode (LED)

And, please see 3 Nd Edu site for the article What is a light-emitting diode?

For additional information, please see PV Education site for the article Bias of PN Junctions, especially paragraph on Diodes under Forward Bias.

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An LED facing a photodiode in a light-tight enclosure is commonly known as a/an:
  • Correct Answer
    Optoisolator.
  • Seven segment LED.
  • Optointerrupter.
  • Infra-red (IR) detector.

An LED facing a photodiode in a light-tight enclosure is commonly known as a/an:

Optoisolator.

As in the word itself, it combines circuit's sections while isolating circuits of different voltages.

See Wikipedia's article on Opto-isolator

Also, see TechTarget site for the article optoisolator (optical coupler or optocoupler) by Katie Terrell Hanna

For additional explanations please see Electronics Hub site for the article Light Emitting Diode Basics

Please see Electronics Tutorials site for the article The Light Emitting Diode

Also, please see Physics and Radio Electronics site for the article Light Emitting Diode (LED)

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What circuit component must be connected in series to protect an LED?
  • Bypass capacitor to ground.
  • Electrolytic capacitor.
  • Correct Answer
    Series resistor.
  • Shunt coil in series.

What circuit component must be connected in series to protect an LED?

Series resistor.

To protect LED's, due to their forward bias current direction, the current itself is protected by a series resistor, to prevent subjections to out-of-parameters current flows.

For additional explanations please see Electronics Hub site for the article Light Emitting Diode Basics

Please see Electronics Tutorials site for the article The Light Emitting Diode

Also, please see Physics and Radio Electronics site for the article Light Emitting Diode (LED)

And, please see 3 Nd Edu site for the article What is a light-emitting diode?

For additional information, please see PV Education site for the article Bias of PN Junctions, especially paragraph on Diodes under Forward Bias.

Last edited by markadlerdallas. Register to edit

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