Why did Joseph Henry use hundreds of turns of insulated wire in his electromagnet?

Joseph Henry used hundreds of turns of insulated wire in his electromagnets to significantly increase their magnetic power.1

By using insulated wire, Henry was able to wrap a large number of turns around the iron core without the wire short-circuiting, which would have occurred if he had used bare wire. This design improvement allowed him to create much stronger magnets than those previously developed by others, such as William Sturgeon, who had used only a few turns of bare wire. Through this innovation, Henry successfully constructed an electromagnet capable of supporting over 2,000 pounds, a world record at the time.12