A hand-held portable speaker hooked up to your new smartphone contains a small electromagnet or voice coil inside of it, as do all devices with speakers. The electromagnet translates the electrical current into sounds you can hear by vibrating the paper cone or diaphragm. The current in the electromagnet controls these vibrations that allow you to hear your favorite songs. Electrical devices that require changing currents use electromagnets.

Electromagnets typically consist of copper wire arranged in a coil around a magnetic metal like iron. An electrical current passes through the wire and creates a magnetic field when juiced with power, centering the magnetic flux on the iron core. Once the current shuts down, the electromagnet ceases to magnetize. By increasing or decreasing the current through the coiled wire, it strengthens or weakens the magnetic field. Permanent magnets don’t have this feature, as they don’t have a current through them and they continuously magnetize at the same level. The controlled electrical current increases the applications of the electromagnet compared with a static and permanent magnet.

Electromagnets help maglev trains function and move, but they also help create the magnetic field of a medical magnetic resonance imager to capture images inside the body not viewable by X-ray machines or other means. A miniature electromagnet inside the read-write head, reminiscent of a record player’s arm and needle, magnetizes individual sectors of the magnetic disk and writes the information in binary code to save it. To create the binary code, 0 or 1, the read-write head simply changes direction, driven by the electromagnet. The hard drive uses the same head to interpret the information written to the disk.

The solenoid valve inside washing machines that turns water off or on is a type of electromagnet. Garbage disposals, microwave ovens and induction cooktops all have electromagnets inside them. Tape recorders, VCRs and DVD players also use electromagnets to record the data.

Electric power lines with large gray canisters have electromagnets inside these transformers to step-down the high-voltage current from the power line to a residence or business. The electromagnet inside the gray transformer makes it possible to transfer the electrical current, which is typically a much higher voltage in the power distribution grid. The site receiving electricity gets it at a lower voltage.