One of our most popular electromagnetism demonstrations is J6-01: Electromagnet With A Bang! We discussed this demonstration in a previous highlight article. But now, you can see it in action in this new video with Landry Horimbere.
A massive block of steel is suspended by an electromagnet, courtesy of a single D-cell flashlight battery. When the switch is flipped to open the circuit, the electromagnet turns off, and the block falls dramatically to the table.
The operation of an electromagnet is based on the discovery that an electrical current generates a magnetic field as it flows through a conductor. By grouping many conductors together in a coil, arranged so that their fields align, we can sum their individual electromagnetic fields into a much stronger one. Thus, we can create a strong electromagnet even from a relatively weak current.
You can also try this out at home and in the classroom with this updated magnet simulator from the PhET collection at the University of Colorado.
The simulator has both permanent magnet and electromagnet options. Flip to the electromagnet tab; you should see, as in the screencap above, a battery connected to a coil, with many magnetic field indicators all around. Controls in the margin let you adjust the number of loops in the coil, and a slider lets you vary the voltage. Both the large magnetic compass and the magnetic field meter can be dragged around the screen to measure at different points. You can also swap the battery out for an AC power supply. Try it out!