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 is the sensing of a vibration as it propagates trough a medium. Without a medium, there can be no sound. The speed of propagation depends on the elasticity and density of the medium, the medium itself is not required to move, it the terms that it is only required to support the propagation of the vibration. Note: