William Sturgeon's first electromagnet, 1825.
© Science Museum / Science & Society Picture Library
Reconstruction made in 1925. In 1825, English inventor William Sturgeon (1783-1850) wound a coil of wire around an iron rod and made one of the first electromagnets. Electromagnets, which are powered by electricity, differ from permanent magnets in that the magnetism can be turned on and off. One terminal of the electromagnet is positively charged and the other is negatively charged, so that when the current is turned on the magnetic field around the wire makes the core magnetic.