Guest Post by Sarah Jensen from the Ask an Engineer series, published by MIT’s School of Engineering
Because magnets do not contain energy—but they can help control it…
In 1841, German physician and physicist Julius von Mayer coined what was to become known as a first law of thermodynamics: “Energy can be neither created nor destroyed,” he wrote. It can, however, be converted from one kind to another—by solar panels that turn sunlight to electricity, or in the transformation of natural gas molecules to the heat that cooks our dinner and heats our homes.
“Magnetism is a force, but it has no energy of its own,” says David Cohen-Tanugi SM ’12. Still, he adds, “magnetism is extremely useful for converting energy from one form to another. About 99 percent of the power generated from fossil fuels, nuclear and hydroelectric energy, and wind comes from systems that use magnetism in the conversion process.”
Every energy generation technology—with the exception of photovoltaics—relies on spinning turbines that put electrons in motion and push them through circuits and generators. “As these charged particles move past magnets inside the turbines, they create a field around them that affects other charged particles,” says Cohen-Tanugi. “This is the magnetic force that converts the energy of wind and coal and nuclear fuel to the electricity that’s sent out into the power grid.” Read more
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