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 can also mean a body of water, like a bay or channel. We can define a sound wave as a disturbance which travels through some medium. Sound is the term to describe what is heard when sound waves pass through a medium to the ear. All sounds are made by vibrations of molecules through which the sound travels. For instance, when a drum or a cymbal is struck, the object vibrates. These vibrations make air molecules move.