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Motors and engines change energy into useful motion

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Bikes get power from you pedaling and using your effort to make it go. Windmills turn because the force of wind pushes them. Horse drawn carriages move because horses pull them. Waterwheels turn from the force of a river or stream flowing. However, how do things move that don’t have humans or nature putting energy into moving them? This is the purpose of engines and motors.

Engines and motors are machines that change energy into useful motion. An energy source, like fuel, is put into the engine and is turned into this motion. Engines and motors allow us to create machines that can run without constant supervision and without humans or nature directly moving the parts of the machine. Although the words engine and motor are often used interchangeably, the word “engine” originally referred to any type of machine that converted any source of energy or fuel into a force, while a “motor” was anything that created motion. Now, we use the word engine to refer to a machine that burns fuel to create motion, while a motor runs on energy sources like electricity and pressurized water that do not get chemically changed when used.


Motors and engines are organized based on the type of energy they use to make motion

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Different types of motors and engines get power from different types of energy. There are many types of engines that all use different kinds of energy, but some common ones are heat engines, hydraulic motors, pneumatic motors, and electric motors. Heat engines use the burning of fuel to power the motor and make movement. They can be found in cars, planes, and trains. Hydraulic motors are machines that use tightly pressurized, or tightly squeezed, liquids to make motion. They are mainly used in large equipment like cranes and construction diggers. Pneumatic motors use pressurized air to create motion. They are now being used in roller coaster launch systems and hand-held tools. Electric motors use electricity from things like a battery or a wall plug to power the engine. They can be found in household appliances and power tools.

The kinds of engines you are likely to come across in everyday life are heat engines and electric motors and are talked about below.


Heat engines burn fuel to create movement

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Heat engines burn fuel to create heat to get power. This is because to get power from a fossil fuel, like coal or gas, you have to burn it. Engines turn the potential, or stored, energy in fossil fuels into motion through controlling this burn. Heat engines are what you will find in most kinds of transportation like cars, planes, trains, and rockets. Within cars and rockets they are called “internal combustion engines”, while planes use engines called turbines.

When a car engine burns gas, it releases a huge amount of energy inside of pistons, which are cylinders with parts that move up and down inside of them. That energy is used to create motion in the car, which is guided to the axles, the part of the car that spins the wheels.


Heat engines create movement in a four-step process: Suck, Squeeze, Bang, and Blow

There are four steps in the process to turn the fuel into movement which can best be remembered by these four words: Suck, Squeeze, Bang, and Blow.

Suck: The fuel mixed with air is forced into a cylinder in the engine when the piston goes down.

Squeeze: No more fuel is allowed to enter the cylinder and the piston goes up, making the space the fuel and air mixture has in the cylinder much smaller.

Bang: At this point a spark plug is set off, igniting the fuel and air mixture. This is where the energy is changing forms and movement is being created. This forces the piston back down. The forcing of the piston back down is the transfer of the energy from the fuel to the car. This piston movement turns the drive shaft of the car. A drive shaft is a part of a car that carries the power to the wheels and makes them turn.

Blow: At the piston goes back to the top of the cylinder, the exhaust is opened and the spent fuel and air mixture exits the engine. Another type of heat engine is a steam engine. Steam engines were the first type of major engine to see a large amount of use and helped to advance the modern world to how it is today. Steam engines also use a piston system, but boil water and use steam to power the engine’s pistons instead of a fuel and air mixture.


Electric motors change electricity into movement

Electricity is used to power electric motors. There are two kinds of electric motors, AC and DC motors. AC motors are powered by AC (alternating current) electric sources like wall plugs. DC motors are powered by DC (direct current) sources like batteries.

Electric motors often use magnetic fields and wire to change the power into motion. A loop of wire is created and put between a north magnetic pole and a south magnetic pole. When a current is run through a magnetic field, a force is created. Therefore, current is then run through the wire loop, generating force. This makes each side of the loop repel the magnets in opposite directions. This movement makes the loop rotate and creates motion.

Electric motors are used in power tools like drills and saws and wall as household appliances like washers and blenders.


Motors are judged by their efficiency

Efficiency measures how much energy the engine makes compared to the highest amount of energy the fuel could produce. To know how well a motor works, you must look at its efficiency value.

If a motor has a high efficiency, the amount of energy that can be used for work is close to the amount in the fuel. This is a well working motor. A motor with low efficiency wastes energy that can be put to better use. Low efficiency motors lose energy through things like heat, friction, sound, and poorly-designed or -fitting parts. These motors are not as well working.

The goal of engineers is to make engines with a higher efficiency. These engines are also cost less to run since they use less fuel to do the same task.


The first engineers were people that worked on engines

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The word “engineer” actually comes from the word “engine” because they first people ever to be called engineers were people that constructed military engines like catapults in the 1380s. By the 1700s people that worked on constructing actual engines like those described above were referred to as engineers. Therefore, the creation of whole engineering fields started with this one machine.


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