Ohm Sweet Ohm

Light one LED without burning it out. That's the first bench. Thirty-four later you'll have built a working binary adder out of relays.

Ohm Sweet Ohm is a real breadboard you can carry around. Push components into the holes, run wires between them, and the circuit is actually simulated: current flows, resistors limit it, and if you skip one your LED burns out in front of you.

You start with a battery, a resistor and one LED, and work up through series and parallel wiring, Ohm's law, dimmer dials, switches, logic gates built from relays, capacitors that hold a circuit open after you let go, binary and hexadecimal, and finally a full adder—the circuit at the heart of every computer that has ever done arithmetic.

Every bench explains the idea behind it in plain language. Why a resistor is needed at all. Why series shares current and parallel shares voltage. Why a capacitor makes a delay you can time with a stopwatch. If you've never touched electronics, start at bench one and it will make sense.

Between benches there's a workshop, and a robot you can name who works there. Clearing benches earns nuts and bolts, which buy hats, paint, visors and antennas for him, and eventually a second robot to keep him company. When you need a break from the learning, you can enjoy dressing him up in whatever combinations you see fit.

Available in English, Korean, Japanese, Spanish and French.

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