About the middle of the previous century our teacher was conducting a Science class on electricity and magnetism. Very elementary stuff. She asked each of us to go home and construct a project that used one or more dry cell batteries and then bring our project back to show in class. The usual mish-mash of door-bell and low-voltage incandescent light circuits were presented for show-and-tell. One unfortunate student was a farm boy. Apparently bare copper wire was a staple around farms in those days. As were steel bolts. So he wound, in random fashion, a large amount of bare copper wire around a largish bolt and brought that to class, seeking to demonstrate the construction of an electromagnet. I don't think he had a battery at home to "test" his creation... which was a "good" thing. So, anyway, when it came time to demonstrate his "electromagnet," using a pair of dry-cells provided by the teacher, the result was a total fail. No magnetism evident from the steel bolt, although the wire did get somewhat warm. We didn't have any test equipment, no voltmeter, no ammeter, not even a pocket compass that could be used to make a crude galvanometer... nada. However I noticed right away what the problem was: no insulation on the wires used to wind his "electromagnet". The poor kid became the laughing stock of our little class because of his blunder. Fortunately no one dwelled on it, and we all went on to study other things, most of the class leaving the mysteries of electricity in the hands of others.
Moral of this story: check to make sure your electromagnet is wound with insulated wire.