Explorables

Standalone interactive pieces: shorter than the book, and meant to be played with.

• How does an LED make light?: Three LEDs on one battery, simulated live: infrared, red and blue. Why each glows one colour, and why a blue one needs more volts than a red one.

• Why do solar panels hate heat?: Two identical solar panels under the same sun, simulated live: one cool, one hot. Why the hot one makes less power: a leak that heat opens, and the voltage it costs.

• Why are your nerves wrapped in fat?: Three nerves race, simulated live: a thin bare one, the same one wrapped in myelin, and a squid's giant one. Why wrapping wins, and which ions carry the signal.

• Why does fast charging slow down near full?: A lithium-ion battery drawn four ways, all driven live by one simulation: the crowd of lithium, the two shelves of its energy, the charging curve, and every species.

• One battery, four pictures: The Daniell cell drawn four ways: particles, the textbook ledger, electron levels, and species voltages, all driven live by one model.