How did William Sturgeon build an early electromagnet?

In 1825, English electrical engineer William Sturgeon demonstrated his first electromagnet, a device that proved foundational to modern technology.12

To build this device, Sturgeon wrapped 18 turns of bare copper wire around a U-shaped iron bar. When he applied an electric current from a single cell, the bar became magnetized and was capable of supporting 9 pounds (4 kilograms) of iron—roughly 20 times its own weight. Crucially, the device demonstrated that the magnetism was temporary; when the current was turned off, the bar lost its magnetic properties.21

Sturgeon’s work built upon the earlier discovery by Hans Christian Ørsted that electric currents produce magnetic effects. While Sturgeon’s design was a significant breakthrough, later researchers like Joseph Henry improved upon the concept by using insulated wire to prevent short-circuiting, allowing for the use of hundreds of turns of wire to create much more powerful magnets.2