This is for all those free Energy fanatics who claim they can light over a hundred LED xmas lights to ‘full brightness’ on a single AA cell.
I put four white LEDs on a small PC board in series, and connected them to a 9VDC wall wart AC adapter, which put out about 15 volts open circuit. Each LED dropped about 3.2 volts, so the total drop added up to 12.8 volts. I put an 82 0hm current limiting resistor in the wire coming out of the inline jack and taped it up with electrical tape. The current, calculated from the voltagedrop across the 82 ohm resistor, was 16 mA. The adapter has no regulation so as the line voltage changed, I saw the current change.
As can be seen from the photos, the LEDs took several minutes to dim after the adapter was unplugged. Free energy! Coming out of nowhere! So I lied. The glow is from the energy stored in the electrolytics inside of the adapter.