How Magnets Work

mri scan

Magnetic resonance imaging (MRI) is an imaging technique used in radiology that uses strong magnetic fields, magnetic field gradients and radio waves to generate images of the organs in the body. Shutterstock/Gorodenkoff

Every time you use a computer, you’re using magnets. If your home has a doorbell, it probably uses an electromagnet to drive a noisemaker. Magnets are also vital components in CRT televisions, speakers, microphones, generators, transformers, electric motors, burglar alarms, cassette tapes, compasses and car speedometers.

In addition to their practical uses, magnets have numerous amazing properties. They can induce current in wire and supply torque for electric motors. Maglev trains use magnetic propulsion to travel at high speeds, and magnetic fluids help fill rocket engines with fuel.


Earth‘s magnetic field, known as the magnetosphere, protects it from the solar wind. According to Wired magazine, some people even implant tiny neodymium magnets in their fingers, allowing them to detect electromagnetic fields.

Magnetic resonance imaging (MRI) machines use magnetic fields to allow doctors to examine patients’ internal organs. Doctors also use pulsed electromagnetic fields to treat broken bones that have not healed correctly. This method, approved by the United States Food and Drug Administration in the 1980s, can mend bones that have not responded to other treatment. Similar pulses of electromagnetic energy may help prevent bone and muscle loss in astronauts who are in microgravity environments for extended periods.

Magnets can also protect the health of animals. Cows are susceptible to a condition called traumatic reticulopericarditis, or hardware disease, which comes from swallowing metal objects. Swallowed objects can puncture a cow’s stomach and damage its diaphragm or heart. Magnets are instrumental to preventing this condition.

One practice involves passing a magnet over the cows’ food to remove metal objects. Another is to feed magnets to the cows. Long, narrow alnico magnets, known as cow magnets, can attract pieces of metal and help prevent them from injuring the cow’s stomach.

People, on the other hand, should never eat magnets, since they can stick together through a person’s intestinal walls, blocking blood flow and killing tissue. In humans, swallowed magnets often require surgery to remove.

Some people advocate the use of magnet therapy to treat a wide variety of diseases and conditions. According to practitioners, magnetic insoles, bracelets, necklaces, mattress pads and pillows can cure or alleviate everything from arthritis to cancer. Some advocates also suggest that consuming magnetized drinking water can treat or prevent various ailments.

Proponents offer several explanations for how this works. One is that the magnet attracts the iron found in hemoglobin in the blood, improving circulation to a specific area. Another is that the magnetic field somehow changes the structure of nearby cells.

However, scientific studies have not confirmed that the use of static magnets has any effect on pain or illness. Clinical trials suggest that the positive benefits attributed to magnets may actually come from the passage of time, additional cushioning in magnetic insoles or the placebo effect. In addition, drinking water does not typically contain elements that can be magnetized, making the idea of magnetic drinking water questionable.


Originally Published: Apr 2, 2007

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