Inside a hair dryer. Motor-driven fan (left) and heating element (right).

Hair Dryer Basics

You can find a hair dryer like this one in almost any drug or discount store. Basic models have two switches, one to turn them on and off and one to control the rate of airflow. Some models have an extra switch that also lets you regulate the temperature of the airflow.

The hair dryer dries your hair by speeding up the evaporation of water from the hair's surface. The hot air emitted from a hair dryer increases the temperature of the air surrounding each strand of hair. Since warm air can contain more moisture than air at room temperature, more water can move from your hair into the air. The increase in temperature also makes it easier for the individual molecules in a water droplet to overcome their attraction to one another and move from a liquid to a gas state.

Since they were first developed, thousands of patents have been issued for different hair dryer designs, but most of them only tweak the outside packaging of the hairdryer so that it looks more aesthetically appealing to you. Aside from the addition of some safety features, the operating system inside hair dryers hasn't changed too much over the years.

A hair dryer needs only two parts to generate the blast of hot air that dries your hair:

  • a simple motor-driven fan
  • a heating element

Hair dryers use the motor-driven fan and the heating element to transform electric energy into convective heat. The whole mechanism is really simple:

  1. When you plug in the hair dryer and turn the switch to "on," current flows through the hair dryer.
  2. The circuit first supplies power to the heating element. In most hair dryers, this is a bare, coiled wire, but in models that are more expensive there can be fancier materials in action, like a tourmaline-infused ceramic coating.
  3. The current then makes the small electric motor spin, which turns the fan.
  4. The airflow generated by the fan is directed down the barrel of the hairdryer, over and through the heating element.
  5. As the air flows over and through the heated element, the generated heat warms the air by forced convection.
  6. The hot air streams out the end of the barrel.

Now that we've got the heat, read on to find out how the hair dryer gets that heat moving.