Sound of the Lorentz Force

The Lorentz Force is felt by the charge particle in an electric current as they pass through a magnetic field, the force felt will always be at right angles to both the direction of the magnetic field and the direction of the current flow. Depending on the country and decade you live in this is also known as the left or right hand rule, if the magnetic field is pointing the X direction and the current is flowing in the Y direction then the current carrying particles feel a force in the Z direction.

By passing a high current audio signal though a short length of aluminum foil, which is suspended in a strong magnetic field, the world's simplest speaker is born. As current flows back and forth the foil is alternately pushed and pulled in such a way that we can hear its flapping as sound. The official name for this is a "Ribbon Speaker," if you were to hook the input of an amplifier to the ribbon and yell into it, it would become a "Ribbon Microphone" instead.