Ohm's law and the LED
Work out which resistor an LED needs, wire it up, and watch the voltages around the loop add up to the supply.
A free lesson from Ohmwork, played entirely in your browser on a real circuit solver — about 20 minutes.
Play this lesson in your browser — no download, no sign-up, and nothing you build is sent anywhere.
The full Ohmwork workshop — in development for Mac and Windows — carries 64 lessons across five courses, six simulated Arduino boards running real compiled sketches, an oscilloscope, and fault-finding practice.