A fan and a hot wire, in that order
What Is Inside a Hairdryer?
A hairdryer is a small fan blowing over a coil of thin wire, and the order of those two parts is what keeps it safe.
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Step 1 of 5
Thin wire resists, and resistance makes heat.
Squeezing the same current through a much thinner wire is hard work, and that work comes out as heat. The coil glows a dull orange while it runs.
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Step 2 of 5
The fan comes first for a reason.
Air is pushed past the coil constantly, carrying heat away as fast as it is made. Without that flow the wire would reach its own melting point in seconds.
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Step 3 of 5
That is why the fan cannot be switched off.
The cool button turns the coil off and leaves the fan running, never the other way round. A blocked inlet is dangerous for the same reason.
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Step 4 of 5
A safety cutout watches the temperature.
A bimetal switch sits right by the coil. If the air stops moving and the temperature climbs, it snaps the power off before anything can catch.
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Step 5 of 5
Hair dries because of the moving air, not the heat.
Warm air can hold more water, but it is the constant sweep of fresh air past your head that carries the water vapour away. Warm still air dries very slowly.
A hairdryer draws around 1,800 watts — more than a fridge, a television and a laptop running together.
The short version
A hairdryer is a fan blowing over a coil of thin resistance wire, and it is the moving air, not the heat, that actually dries your hair.
Try it yourself
Switch to the cool setting. Hair still dries, just more slowly — proof that the airflow is doing most of the work.
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