Energy and society

What does physics have to do with food? The answer is far more important today than it was even 50 years ago. A healthy diet has a daily energy content of 2,000 Calories, or 8.4 million joules. This energy must come from food, and the food required to feed Earth’s human population has increased dramatically. Consider that there were about 1 billion people on Earth in 1800. By 1927 the population had doubled to 2 billion. By 1960 there were 3 billion people. By 1974 there were 4 billion, and by 2012 the world population was 7 billion and growing. Yet the amount of land and sunlight available for farming is the same today as it was 200 years ago. Read the text aloud
Since 1950 the world population has almost tripled. Yet, according to the U.S. Geological Survey, the amount of land and water devoted to growing food has actually decreased because of urbanization and soil degradation. How do we feed more people with less farmland? The answer is a widespread change from traditional methods of farming to more energy-intensive, high-yield agriculture. This largely took place between 1950 and 2000, a period that has been dubbed the “green revolution.” Read the text aloud Show Technology and agriculture
How to read a home electricity billYour family’s monthly home electricity bill shows how much electrical energy you used in the past month (measured in kilowatt-hours or kWh) and charges for the generation and transmission of that electricity. Electricity generation costs are for the power plant—hydroelectric, coal-fired, natural gas, etc.—that produced the power in the first place. Electricity transmission costs cover the high-voltage power lines, the power lines on your street, the transformers, and so on. In the example at right, the delivery costs (9.4 cents/kWh) are actually higher than the generation costs (7.0 cents/kWh)! Read the text aloud
Have class volunteers bring in a copy of their most recent electricity bills. Each student can extract and communicate the information in his or her bill, such as energy used per month, cost per kilowatt-hour, and change in consumption compared to the previous month. Read the text aloud
How to read an energy guide label for an applianceMajor home appliances are sold with an “EnergyGuide” label that indicates their expected energy consumption per year. This standardized labeling compares the energy usage of a particular appliance with similar models produced by the same or other companies. In the example at right, this refrigerator will cost approximately $67 to operate per year and consumes somewhat more energy than the average of other models. Read the text aloud Show Energy Star
Research clothes dryers either on the Internet or in a local store to compare the energy consumption of each appliance. In class, each student should verbally summarize the content of a label, such as its annual energy consumption, yearly operating cost, and how it compares to similar models. Which models are the most energy efficient? Read the text aloud Show Comparing apples and oranges?
In the EnergyGuide illustration above, what is the cost of electricity assumed in producing this label? Show
Which of the following are reasons why total agricultural production has increased over the past 100 years?
  1. more mechanized farm equipment
  2. better irrigation techniques
  3. better methods to deal with insects
  4. all of the above

Previous Page Next Page269