How Fuel Cells Work. Polymer Electrolyte Membrane (PEM) fuel cells used in automobilesâalso called Proton Exchange Membrane fuel cellsâuse hydrogen fuel and oxygen from the air to produce electricity. The diagram and animation below show how a PEM fuel cell works.
Sound is what happens when you transmit vibrations of energy through that matter. Sound is made up of wave vibrations. When you talk aloud, the motion of your vocal cords causes the air to vibrate. Air is made up of molecules, and as those air molecules vibrate, they hit each other.
Sound (in air) is made when air molecules vibrate and move (away from the vibrating source) in a pattern called waves, or sound waves. Sound is a mechanical, longitudinal wave (that moves in all directions) and travels in waves of compressions and rarefactions (expansion) as it successively passes through a medium.