Element 3: General Radiotelephone

effective 6/25/2009

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3-C-027: Light Emitting Diodes

3-27C1: What type of bias is required for an LED to produce luminescence?

Forward bias.

Reverse bias.

Logic 0 (Lo) bias.

Logic 1 (Hi) bias.



3-27C2: What determines the visible color radiated by an LED junction?

The materials used to construct the device.

The color of a lens in an eyepiece.

The amount of voltage across the device.

The amount of current through the device.



3-27C3: What is the approximate operating current of a light-emitting diode?

20 mA.

5 mA.

10 mA.

400 mA.



3-27C4: What would be the maximum current to safely illuminate a LED?

20 mA.

1 amp.

1 microamp.

500 milliamps.



3-27C5: An LED facing a photodiode in a light-tight enclosure is commonly known as a/an:

Optoisolator.

Seven segment LED.

Optointerrupter.

Infra-red (IR) detector.



3-27C6: What circuit component must be connected in series to protect an LED?

Series resistor.

Bypass capacitor to ground.

Electrolytic capacitor.

Shunt coil in series.





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