I bought a cheap string of LEDs in the supermarket (the christmas decorationny type) and just out of curiosity I'm trying to figure out how it works, because I can't understand how it doesn't short itself.
It consists of a basic holder for two AA batteries with an on/off switch, and 20 tiny but bright white LEDs on two wires that lead out of the holder. The wires connect to one end of the first LED, and on the other side of the LED two wires lead to the next LED, so each LED has four "legs". The wires on the end of the very last LED simply connect to each other.
The wires themselves are not insulated, (only the LEDs are, they appear to be dipped in some kind of transparent silicone), which What's weird to me because the positive and negative wires are touching all along the length of the strip. Also, you can scrunch up the wires and touch each bit of wire to every other bit of wire, and it still works. In fact, the two wires that come out of the battery holder appear to be touching. How is it not immediately shorting out the batteries, or causing a short when you scrunch it up?
Best Answer
The LEDs seems to be mounted in parallel with each other. The four legs are the same two wires running across the transparent blob, which is there to give the mounting some physical strength, I believe.
simulate this circuit – Schematic created using CircuitLab
The wires have to be insulated. But the insulation must be very thin in this case. Or, maybe, it is enameled copper wire. Otherwise, as you said, the circuit would be shorted out. If you want to take the proof, try to scrape the insulation with a sharp knife or blade and test its continuity.