Transa

Meet Transa, a transformer who trades voltage for current using nothing but coils and a changing field.

A transformer has two coils wound on a shared iron core. Alternating current in the primary coil makes a changing magnetic flux in the core, and by Faraday's law of induction that changing flux induces a voltage in the secondary coil. Each turn of wire picks up the same voltage, so the voltages are in the ratio of the numbers of turns: V_s/V_p = N_s/N_p.

Ten times as many turns on the secondary gives ten times the voltage. In an ideal transformer, power in equals power out, so the current is ten times smaller.

This is why power grids use high voltages for long-distance transmission: the same power at lower current wastes far less energy as heat in the lines. Transformers then step voltage back down for homes, and small ones in chargers step it down further.

Transformers only work with changing current; steady DC induces nothing. Real transformers lose a few percent of their power to resistance in the windings and to the core.