1. POWER

2. Power –Power measures how quickly work is done –Power systems are the machines that use energy to perform work –They are found in automobiles, jet airplanes and the tape drive of a cassette player –1 hp = 550 ft – lbs/sec or 1 hp = 33,000 ft – lbs/min –1 hp = 746 Watts

3. Power Systems –They have two major parts --- engine and transmission –An engine is a machine that uses energy to create mechanical force and motion --- automobiles, trucks, jet aircraft, submarines and home appliances –A transmission, or drive, is a device that transfers force from one place to another or changes its direction --- belts, pulleys, chains and gears –A transmission may also increase/decrease the force or divide it into smaller parts –People in around 600 BC used simple engines using the energy of animals and the wind --- grinding grain, pumping water –Today, engines uses the energy in fuels. They change the energy stored in fuels into mechanical force and motion –The fuel in today’s engines is portable

4. Transmission Engine

5. Engines –Automobiles, rockets, factories –Types : external, internal combustion engines, reaction engines, electrical motors and nuclear reactors  External Combustion Engines –The fuel is burned in a separate chamber –Expanding gas builds up pressure and applies force on a piston or turbine –Force on a piston gives a back-and-forth (reciprocating) motion –Force on a turbine gives a rotational (turning) motion –A flywheel and connecting rod are used to change the movement of the piston into rotary motion –The flywheel builds up momentum and smoothes out the rotary motion –In a railroad locomotive, the drive wheels are connected to steam pistons

8. Engines  Internal Combustion Engines –First successful engine was invented by Otto in 1876 –Fuel is burned in a closed chamber --- combustion chamber –Burning fuel becomes expanding gas and pushes a piston –Piston is connected by a rod to a crankshaft –Crankshaft changes the piston’s reciprocating motion into rotary motion –Small engines are used in lawn mowers, portable generators and snow throwers etc –No spark plugs is used in a diesel engine. They are used in large trucks and ships etc –When the piston or flywheel makes an object (the load) move, work is done. In this way, the engine delivers power

10. Engines  Internal Combustion Engines –Four Stroke Cycle  Intake Stroke  Compression Stroke  Power Stroke  Exhaust Stroke