Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What is the relationship captured by the concept of efficiency?

1. The difficulty of using simple machines

2. The relationship between energy input and energy output

3. The speed at which work is performed

4. The amount of friction in a machine

The correct answer is: The relationship between energy input and energy output

The concept of efficiency fundamentally describes how well a system converts input energy into useful output energy. It is a measure of the effectiveness of a machine or process in utilizing energy, comparing the energy that goes into the system to the energy that comes out as useful work. In mathematical terms, efficiency is often expressed as a percentage, calculated by dividing the useful output energy by the total input energy and multiplying by 100. In the context of machines, a high efficiency indicates that most of the input energy is converted into useful work, while a lower efficiency suggests that a significant portion of energy is lost, often due to factors like heat, sound, or friction. This relationship highlights not only the performance of an individual machine but also allows for the comparison of different machines or systems on how well they convert energy.