Electromagnets THE DISCOVERY OF a magnetic field around a current-carrying wire(pp. 26-27), and the fact that a coil of wire had a greater magnetic effect than a single turn, led to fascinating new gadget that made lecture audiences gasp with surprise. In 1825 William Sturgeon(1783-1850 wound a coil of wire around an iron rod and built one of the first electromagnets. An electromagnet differs from the usual permanent magnet its magnetism can be turned on and off. It usually consists of insulated electrical wire wound around a piece of iron, known as the core. Switch on the current, and the magnetic field around the wire makes the core behave as a magnet. It attracts iron-containing substances in the usual way. Switch off the electricity, and the magnetism disappears. Sturgeon built the electromagnets as demonstration models for his lectures.