USEFUL ENERGY AND EFFICIENCY

EFFICIENCY

* A measure of how effectively a machine converts input energy into useful output energy

* efficiency = useful work output

                    total work input

USEFUL ENERGY AND EFFICIENCY

ENERGY INPUT 

* The initial energy source

* Input​ refers to the amount of energy put into a device, and ​ output​ refers to the amount of energy that comes out. A device may change the type of energy but not the amount. For example, a light bulb's input energy is the form of electrical energy, and its output energy is in the form of light and heat.

USEFUL ENERGY AND EFFICIENCY

PERCENTAGE EFFICIENCY

* Efficiency expressed as a percentage

* percent efficiency = useful work output  X 100%

                     total work input

(Note: when calculating efficiency, the units cancel. Efficiency, whether shown a a percent or not, has no units)

USEFUL ENERGY AND EFFICIENCY

USEFUL ENERGY

* Energy needed to perform a task 

* Energy entering a system is called the input energy. The energy is transferred in a system to provide a useful output energy. The useful output is therefore less than the input energy as some of the output energy is wasted. An example is a light bulb where the input is electricity and the useful output is light.

USEFUL ENERGY AND EFFICIENCY

USEFUL ENERGY OUTPUT

* Energy needed to do work 

* The Law of conservation of energy states that energy can be neither created nor destroyed; it can only be transformed. When efficiencies of energy devices are examined, there is sometimes much more energy put into the device than is converted into useful form of energy.

USEFUL ENERGY AND EFFICIENCY

USEFUL WORK OUTPUT

* Work a machine is supposed to do 

* In physics, work output is the work done by a simple machine, compound machine, or any type of engine model. In common terms, it is the energy output, which for simple machines is always less than the energy input, even though the forces may be drastically different.