Lesson 4.1: Energy Efficiency

Each generation of people in our country are more productive than the last.  We use more machines, bigger machines, faster machines to do more work per person than ever before.  Farmers used to struggle to farm a few hectares of land.  Farmers today can farm thousands of hectares.  What effect does this have on our use of energy and the environment? 

Read Spinning Our Wheels: Energy and Efficiency on page 145 of your textbook to begin your study of this interaction. Then, answer the following questions.

Question 1. The car is stuck in the snow.  Where is the energy being wasted?

Question 2. Are any machines 100% efficient?

Question 3. What are three ways that energy is lost when a machine is used?

Question 4. Which is always greater, the work input or the useful work output? Explain.
                                

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. The car is stuck in the snow.  Where is the energy being wasted?

The engine is running, the tires are spinning, the car is not moving.  Energy is being wasted in all these situations because no useful work is being done.  When energy is used but useful work is not done, then the energy is wasted.

Question 2. Are any machines 100% efficient?

No machines are 100% efficient.  All machines waste some energy, usually through friction.

Question 3. What are three ways that energy is lost when a machine is used?

The three ways that machines lose energy are
- friction
- heat
- incomplete combustion

Question 4. Which is always greater, the work input or the useful work output?  Explain.

The work input is always greater than the useful work output.  Always some energy is wasted when work is done.  Even your body wastes energy when you do work.  The evidence is that your body heats up when you do work.


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