HowStuffWorks Autopsy: Inside a Hair Dryer

Today the hair dryer is one of those household appliances that many of us just can't live without. We use them every day.


There is a surprising amount of stuff crammed inside a typical hair dryer. But underneath all the wires, there are really just a few essential pieces:

This hair dryer has:

  • A plastic screw-shaped fan blade. The blade is built like a small waterwheel. It pushes air the same way a waterwheel pushes water.

  • A simple electric motor, connected to the fan blade.

  • A long strand of coiled nichrome wire. This metal wire is like the thin wires inside a toaster or a light bulb. It's made of metal that does not conduct electricity very well, so when you run electricity through the wire, the wire's high resistance to electricity makes it heat up. (This is the same thing that makes a light bulb light up.)


  • Insulating boards covered in mica. Mica is a type of mineral that does not conduct heat well. The nichrome wire is wrapped around this insulating board, to keep the hot wire from starting a fire in the hair dryer.

  • An insulating sleeve, also covered in mica, goes around the wire and insulating boards.

  • Air inlets in the body of the hair dryer, covered by safety screens. The safety screens stop hair from being sucked into the hair dryer.

  • An electrical circuit running power from an electrical outlet to the coiled wires and the electric motor.

  • A power button that opens and closes an electrical switch in the circuit.

  • Two sliding power setting switches that let you adjust the motor speed and heat level. The switches are connected to a bunch of smaller circuits in the big circuit. By sliding the switch, you redirect the electrical current to a different smaller circuit. The "high setting" circuits boost the current, to make the wires heat up more or make the fan turn faster. The "low setting" circuits decrease the current, to turn down the heat or slow down the fan.

And here's how it all comes together:

  • When you plug in the hair dryer and switch it on, electricity flows to the coiled wires, heating them up.
  • Electricity also flows through the electric motor, which spins the fan blade.
  • The spinning fan blade moves air through the intake port, down the hair dryer's barrel.
  • Heat rising from the coil warms the flowing air.
  • The hot air streams out of the barrel's end.
  • The hot air increases the temperature of the air surrounding each strand of hair, speeding up the evaporation process. The heat also makes it easier for the individual molecules in a water droplet to split apart, forming vapor. The liquid water is removed, and your hair dries!