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A beginner battery-powered LED circuit

These exercises use loose AA cells or disconnected, unpowered passive parts only. Do not work on household wiring, mains supplies or high-voltage equipment. Never connect current-mode probes across a battery. Stop if a battery is damaged, leaking or hot.

3 V+−330 ΩLED+−
3 V holder → 330 Ω resistor → red LED → holder. Assemble with batteries removed.
  1. Use two undamaged AA cells in a 3 V holder, a red LED with a typical forward voltage near 2 V, and a 330 Ω resistor rated at least 0.25 W. Check the LED datasheet; other colours may need a different design.
  2. With batteries removed, connect holder + → resistor → LED anode (+) → LED cathode (−) → holder −. The longer lead often marks anode; confirm with the datasheet and flat-side marking. Keep bare connections apart.
  3. Insert batteries briefly to test, then remove them after use. Current is approximately (3 − 2)/330 = 0.003 A, or 3 mA; actual values vary. Never omit the resistor or short the holder. If anything gets hot, disconnect immediately.

Related explanations

LEDVolts (V)Resistance (Ω)

Official sources