HULTON ARCHIVE/GETTY IMAGESGETTY IMAGES Topic 7: Machines Throughout History

 What are some reasons machines have changed through history?  Technological advancements  Changes in society  Societal/environmental concerns

The Steam Engine  Invented in late 18 th century  Burns a fuel like coal or wood to change water to steam outside the engine (external combustion)  When the water changes from liquid to gas it expands a lot (2,000 L of water = 2,000,000 L of steam)  The pressure of the steam allows it to push the pistons  Steam is a high quality form of energy and it is easily transferred to mechanical systems  How steam engines work How steam engines work

The Internal Combustion Engine  Fuel is burned inside the engine  More efficient, smaller, lighter  Has 4, 6 or 8 pistons, not all pistons are at the same steps at same time  the internal combustion engine the internal combustion engine  Car engines Car engines