This is a picture of a speaker that uses a variable resistor in the sound knob to control the volume of the sound it produces. The resistance on the electrons flowing through the speaker changes as the knob is turned. When the knob is turned, a strip of metal or other conducting substance is moved, forcing the electrons to travel a longer path than before. According to the resistance equation, extending the path also increases resistance. When resistance is increased, less electrons reach their destination per second and less sound is produced.

The Physics of an Air Filter

This is a picture of an air filter in my house that is meant to capture harmful materials in the air such as dust, cotton, and pollen. The filter is able to do this through the use of technology that is related to what we are learning in Physics right now. Near the front of the filter is a grill, which is called the "corona discharge" and is meant to ionize particles in the air. This electrical field gives extra electrons to the neutrally charged particles in the air. Because dust and other harmful substances are usually large, they are the ones who gain the negative charge produced by the "corona discharge." Further into the filter there is a metal plate with a strong positive charge, to which the now charged particles in the air are attracted to. With most of the harmful materials gone, clean air can flow from the top.