LED

A diode that lights up when current flows.

Schematic letter: D
Unit / key rating: Forward voltage (V), current (mA)

Pinout

Anode (+, long lead): Connects to the positive side.
Cathode (−, short lead): On the flat side of the body.

Real photos

What is it for?

An LED (Light Emitting Diode) is a diode that emits light. It passes current in one direction only and glows in proportion to that current.

Each color has a different forward voltage: about 2 V for red and about 3 V for blue and white. Standard 5 mm LEDs run at 10–20 mA.

Things to watch out for

⚠ Never connect an LED straight to a battery; always use a series resistor. You can try it on the simulation page.
⚠ Resistor calculation: R = (Vsupply − Vled) / I

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