Diode
The schematic symbol for a light emitting diode, (LED), is shown on the left and the schematic for a diode is shown on the right.
A diode is an electrical component that allows current to flow in only one direction. A diode consists of two leads called the cathode and the anode. The anode is the lead attached to the triangular shape above and the cathode is the lead attached to the horizontal bar. The cathode on an actual diode is often indicated with a different colored stripe on the component.
A diode will not conduct until its anode’s potential is a certain number of volts higher than the cathode’s. This amount varies based on the type of diode. When the diode conducts, current can only flow from the positive anode to the negative cathode.
When a diode conducts, it can emit light. Diodes that are specially manufactured to produce light are called light emitting diodes, (LEDs). They are often used for indicator lights in electronic instruments.
Video: Make a homemade LED
Diodes on Wikipedia
http://en.wikipedia.org/wiki/Diode
http://en.wikipedia.org/wiki/Light_emitting_diode
Exam Questions
What electronic component allows current to flow in only one direction?
A. Resistor
B. Fuse
C. Diode
D. Driven Element
How is a semiconductor diode's cathode lead usually identified?
A. With the word "cathode"
B. With a stripe
C. With the letter "C"
D. All of these choices are correct
What does the abbreviation "LED" stand for?
A. Low Emission Diode
B. Light Emitting Diode
C. Liquid Emission Detector
D. Long Echo Delay
What are the names of the two electrodes of a diode?
A. Plus and minus
B. Source and drain
C. Anode and cathode
D. Gate and base
What is component 8 in figure T2?
A. Resistor
B. Inductor
C. Regulator IC
D. Light emitting diode
Which of the following is commonly used as a visual indicator?
A. LED
B. FET
C. Zener diode
D. Bipolar transistor