LED stands for light-emitting diode, which means that much like their diode cousins, they’re polarized. In other words, they only work in one direction. There are a few ways to identify the positive (anode) and negative (cathode) pins/leads/legs on an LED.
1. Find the longer leg, which should indicate the positive, anode pin.
2. If someone’s trimmed the legs, try finding the flat edge on the LED’s outer casing. The pin nearest the flat edge will be the negative, cathode pin.
3. Look inside the lens where the leads extend up. One side is much larger than the other. This is called the anvil and is connected to the negative lead.
LED Circuit Diagram Symbol
Let's learn about 8 Engineering Fields by playing some fun and educational student-created Scratch games!
Click on the image to the right to be directed to the Scratch Studio of Student games from 2017-18.
Great Websites with "Career Profiles" for Several Engineering Disciplines: