Hands-on Activity: Watt Meters to Measure Energy Consumption

Contributed by: Office of Educational Partnerships, Clarkson University, Potsdam, NY

A variety of electrical kitchen appliances that inlcude a mixer, a coffee maker and a sandwich maker.
How much energy and power do electrical devices generate?
copyright
Copyright © Wikiedia Commons http://upload.wikimedia.org/wikipedia/commons/1/17/Small_appliance.jpg

Summary

Students use watt meters to measure the power required and calculate energy used from various electrical devices and household appliances.
This engineering curriculum meets Next Generation Science Standards (NGSS).

Engineering Connection

Evaluating energy consumption is the first step engineers take when trying to reduce energy consumption. This step is part of the "understand the problem" and "gather information" steps in the problem solving spiral (and the engineering design process).

Learning Objectives

After this activity, students should be able to:

  • Calculate energy use.
  • Analyze how changing behaviors and appliances affects the amount of energy used.

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Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

  • Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation. (Grade 6) Details... View more aligned curriculum... Do you agree with this alignment?
  • Solve unit rate problems including those involving unit pricing and constant speed. (Grade 6) Details... View more aligned curriculum... Do you agree with this alignment?
  • Use ratio reasoning to convert measurement units; manipulate and transform units appropriately when multiplying or dividing quantities. (Grade 6) Details... View more aligned curriculum... Do you agree with this alignment?
  • Fluently divide multi-digit numbers using the standard algorithm. (Grade 6) Details... View more aligned curriculum... Do you agree with this alignment?
  • recognize and apply mathematics in contexts outside of mathematics (Grades Pre-K - 12) Details... View more aligned curriculum... Do you agree with this alignment?
  • work flexibly with fractions, decimals, and percents to solve problems (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • understand and use ratios and proportions to represent quantitative relationships (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • use the associative and commutative properties of addition and multiplication and the distributive property of multiplication over addition to simplify computations with integers, fractions, and decimals (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • select appropriate methods and tools for computing with fractions and decimals from among mental computation, estimation, calculators, or computers, and paper and pencil, depending on the situation, and apply the selected methods (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • model and solve contextual problems using various representations, such as graphs, tables, and equations (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • understand both metric and customary systems of measurement (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • understand relationships among units and convert from one unit to another within the same system (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • select and apply techniques and tools to accurately find length, area, volume, and angle measures to appropriate levels of precision (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • use observations about differences between two or more samples to make conjectures about the populations from which the samples were taken (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Develop descriptions, explanations, predictions, and models using evidence. Students should base their explanation on what they observed, and as they develop cognitive skills, they should be able to differentiate explanation from description--providing causes for effects and establishing relationships based on evidence and logical argument. This standard requires a subject matter knowledge base so the students can effectively conduct investigations, because developing explanations establishes connections between the content of science and the contexts within which students develop new knowledge. (Grades 5 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Think critically and logically to make the relationships between evidence and explanations. Thinking critically about evidence includes deciding what evidence should be used and accounting for anomalous data. Specifically, students should be able to review data from a simple experiment, summarize the data, and form a logical argument about the cause-and-effect relationships in the experiment. Students should begin to state some explanations in terms of the relationship between two or more variables. (Grades 5 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Communicate scientific procedures and explanations. With practice, students should become competent at communicating experimental methods, following instructions, describing observations, summarizing the results of other groups, and telling other students about investigations and explanations. (Grades 5 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Use mathematics in all aspects of scientific inquiry. Mathematics is essential to asking and answering questions about the natural world. Mathematics can be used to ask questions; to gather, organize, and present data; and to structure convincing explanations. (Grades 5 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Mathematics is important in all aspects of scientific inquiry. (Grades 5 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei, and the nature of a chemical. Energy is transferred in many ways. (Grades 5 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Electrical circuits provide a means of transferring electrical energy when heat, light, sound, and chemical changes are produced. (Grades 5 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Science influences society through its knowledge and world view. Scientific knowledge and the procedures used by scientists influence the way many individuals in society think about themselves, others, and the environment. The effect of science on society is neither entirely beneficial nor entirely detrimental. (Grades 5 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Technology influences society through its products and processes. Technology influences the quality of life and the ways people act and interact. Technological changes are often accompanied by social, political, and economic changes that can be beneficial or detrimental to individuals and to society. Social needs, attitudes, and values influence the direction of technological development. (Grades 5 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Fluently divide multi-digit numbers using the standard algorithm. (Grade 6) Details... View more aligned curriculum... Do you agree with this alignment?
  • Fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation. (Grade 6) Details... View more aligned curriculum... Do you agree with this alignment?
  • Solve unit rate problems including those involving unit pricing and constant speed. (Grade 6) Details... View more aligned curriculum... Do you agree with this alignment?
  • Use ratio reasoning to convert measurement units; manipulate and transform units appropriately when multiplying or dividing quantities. (Grade 6) Details... View more aligned curriculum... Do you agree with this alignment?
  • Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
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Materials List

Each group needs:

  • 1 electrical appliance, such as a blender, drill, electric tooth brush, cell phone, phone charger, computer or laptop, copier, overhead projector, TV, boom box, holiday lights (old, big incandescent ones and new LED type); groups rotate through these items
  • watt meter (for example, do an Internet search for "Kill-A-Watt EZ Plug Power Meter" or "Watts Up Portable Plug In Power Meter," $20-$100 each)
  • Student Worksheet, one per student

To share with the entire class:

  • Enough extension cords/power strips so that all appliances can be plugged in. Especially note how much space the watt meter takes; on most standard wall outlets it is not possible to plug in two simultaneously.

Introduction/Motivation

How do you use energy in your homes? (Expect students to be good at answering this by now!) We generally require both heat (often directly from fossil fuels) and electric power for appliances, entertainment, etc. In this class, we'll focus on the electric energy (really electromagnetic energy) used in typical households. Recall the basic concepts we learned regarding power and energy:

  1. energy = power x time, (units: kWh = W/1000 x hours)

OR

  1. power = energy /time (units: W = (kWh)1000 / h)
  2. power = volts x amps (P= I V)
  • volts: a measure of potential for electricity; such as the height of water behind a dam (120 V = standard household voltage in the US).
  • current: a measure of the flow of electricity, such as the flow rate of water through the dam

How do we know how much electricity an appliance is consuming?

  • Look at the appliance rating – watts? Amps? Watts = amps x volts (It is helpful to have examples, such as a hair dryer, to show this.)
  • Look at tables of "average" wattage. (Note the age of the appliance, such as a refrigerator, and refer to tables in the Home Energy Audit activity.)
  • Reinforce concepts:
  1. energy = power x time,
  2. (kWh = W/1000 x hours)
  3. so appliances that are used for a long time but at a lower wattage might consume the same energy as appliances used for short time periods at high wattage (power)

Procedure

Before class:

  • Distribute the appliances and watt meters around the room, making sure each has access to an electrical outlet.

With the students:

  • If students have never used watt meters, show them how to use them.
  • Complete the watt meter activity. Use the watt meter (distribute, play with these with various devices – hair dryer, microwave, coffee pot, computer, etc.) Suggst that students measure power draw when appliances are off as well as on.
  • Discuss findings, including leaking electricity.
  • Distribute the Home Energy Audit activity; explain that they can enter data onto the hard copy provided or use the Excel spreadsheet. Students can also enter data into the Central Maine Power version that is menu-driven; see http://www2.cmpco.com/EnergyCalculator/input.html.
  • How much does electricity cost? Provide average electricity cost or look at energy bills to determine current and local costs for your community.
  • Conclude by carefully reviewing with students what they need to accomplish with the home energy audit homework and explain why it is so important for their semester project. (They need to fully understand the problem before trying to solve it.)

Attachments

Assessment

Worksheets: Collect and examine student worksheet to assess if they were able to complete the activity and calculate energy consumption accurately.

Other Related Information

This activity was originally published by the Clarkson University K-12 Project Based Learning Partnership Program and may be accessed at http://www.clarkson.edu/highschool/k12/project/energysystems.html.

Contributors

Jan DeWaters; Susan Powers; and a number of Clarkson and St. Lawrence University students in the K-12 Project Based Learning Partnership Program

Copyright

© 2013 by Regents of the University of Colorado; original © 2008 Clarkson University

Supporting Program

Office of Educational Partnerships, Clarkson University, Potsdam, NY

Acknowledgements

This activity was developed under National Science Foundation grant nos. DUE 0428127 and DGE 0338216. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.

Last modified: August 4, 2017

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