Introduction to TechnologyChapter 21:
Transportation PowerChapter SummariesSection 21.1
Much of our useful power comes from engines. Engines use fuel as an energy source. The world’s first engine was a steam engine used to pump water from coal mines. Steam engines are external combustion engines. Section 21.2
Gasoline engines are internal combustion engines. They use pistons that slide up and down inside a cylinder. Each up or down motion of the piston is a stroke. This motion is converted to rotary motion by a crankshaft. Diesel engines are best suited for heavy work. Rocket engines carry oxygen as well as fuel so they can travel in space. Section 21.3
Many trains are powered by electric motors. Some locomotives use diesel engines to turn generators that produce electricity. The hybrid car runs on an electric motor and a gasoline engine. Fuel cell cars convert hydrogen to electricity. Their emission is water.  | 
