The core principle is electromagnetic induction: as a coil rotates within a magnetic field and continuously cuts across magnetic field lines, free electrons within the coil are "pushed" to flow in a specific direction, thereby generating an electric current.
The faster the crank is turned, the stronger the current and the brighter the light.
The direction of the induced current depends on the direction of the conductor's movement and the direction of the magnetic field.
A hand-cranked generator primarily consists of a permanent magnet (stator) and a coil (rotor); turning the handle spins the coil to generate electricity. Some models also incorporate a commutator to convert the output from alternating current (AC) to direct current (DC).
Optimized rare-earth permanent magnet generators can achieve an energy conversion efficiency of over 60%; cranking the handle for just one minute stores enough power to operate the radio for 10 to 15 minutes, fully meeting the low-power requirements of emergency situations.