Please provide a rating, it takes seconds and helps us to keep this resource free for all to use
Welcome to our Physics lesson on Output and Input Power, this is the second lesson of our suite of physics lessons covering the topic of Power and Efficiency, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
It is quite impossible that the entire energy produced by a source converts into work done by the system. For example, if we consider the example of the previous paragraph, it is clear that the energy delivered by the source is not 300 J but much more as some part of it, goes for other purposes, such as to overcome friction etc.
Therefore, the power we calculate through the equation (1) represents the output power, or the power that goes for doing work. Output power is often referred as the useful power because only this part is useful for people who manage the system.
On the other hand, if we divide by time the total energy produced by the source, we obtain the total or input power. If we know how to calculate the total energy (or if the value of total energy is given), we calculate the total (input) power using the equation
It is obvious that the input power has always a greater value that the output power (at most they are equal) because the total energy produced by the source is always greater than the part of it that converts into work.
Theoretically, output and input power can be equal only when the entire energy produced is converted into work. However, this is practically impossible as some of the energy produced turns into other undesirable forms (look at the Physics tutorial "Elastic Potential Energy. Combination of Springs"). As a result, we have
and
The energy lost during the process, is often referred as Wasted Energy (Ew). Therefore, it is obvious that in a system,
You have reached the end of Physics lesson 5.5.2 Output and Input Power. There are 3 lessons in this physics tutorial covering Power and Efficiency, you can access all the lessons from this tutorial below.
Enjoy the "Output and Input Power" physics lesson? People who liked the "Power and Efficiency lesson found the following resources useful:
Please provide a rating, it takes seconds and helps us to keep this resource free for all to use
We hope you found this Physics lesson "Power and Efficiency" useful. If you did it would be great if you could spare the time to rate this physics lesson (simply click on the number of stars that match your assessment of this physics learning aide) and/or share on social media, this helps us identify popular tutorials and calculators and expand our free learning resources to support our users around the world have free access to expand their knowledge of physics and other disciplines.