A current of great electromotive force (intensity or voltage) passed through the coil D, induces, by means of the core and frame, a current of enormous quantity (volume or amperage), but very small electromotive force, in the metal in the trough.
The pulses are of high voltage and low amperage, which makes them, like static electricity, safe but an unpleasant experience.
When choosing an electric heater, you must consider voltage, amperage, and circuit breaker requirements.