Hands-on Activity Watt Meters to Measure Energy Consumption

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Quick Look

Grade Level: 8 (6-8)

Time Required: 45 minutes

Expendable Cost/Group: US $0.15

This activity uses some non-expendable (reusable) items such as watt meters, electrical appliances and extension cords; see the Materials List for details.

Group Size: 3

Activity Dependency:

Subject Areas: Physical Science, Science and Technology

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 aligns to 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.

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.

  • Energy may take different forms (e.g. energy in fields, thermal energy, energy of motion). (Grades 6 - 8) More Details

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  • Use mathematical representations to describe and/or support scientific conclusions and design solutions. (Grades 6 - 8) More Details

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  • Collect data to produce data to serve as the basis for evidence to answer scientific questions or test design solutions under a range of conditions. (Grades 6 - 8) More Details

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  • Typically as human populations and per-capita consumption of natural resources increase, so do the negative impacts on Earth unless the activities and technologies involved are engineered otherwise. (Grades 6 - 8) More Details

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  • Fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation. (Grade 6) More Details

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  • Solve unit rate problems including those involving unit pricing and constant speed. (Grade 6) More Details

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  • Use ratio reasoning to convert measurement units; manipulate and transform units appropriately when multiplying or dividing quantities. (Grade 6) More Details

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  • Fluently divide multi-digit numbers using the standard algorithm. (Grade 6) More Details

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  • recognize and apply mathematics in contexts outside of mathematics (Grades Pre-K - 12) More Details

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  • 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) More Details

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  • 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) More Details

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  • Mathematics is important in all aspects of scientific inquiry. (Grades 5 - 8) More Details

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  • 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) More Details

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  • Electrical circuits provide a means of transferring electrical energy when heat, light, sound, and chemical changes are produced. (Grades 5 - 8) More Details

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  • Fluently divide multi-digit numbers using the standard algorithm. (Grade 6) More Details

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  • Fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation. (Grade 6) More Details

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  • Solve unit rate problems including those involving unit pricing and constant speed. (Grade 6) More Details

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  • Use ratio reasoning to convert measurement units; manipulate and transform units appropriately when multiplying or dividing quantities. (Grade 6) More Details

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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.

Worksheets and Attachments

Visit [www.teachengineering.org/activities/view/cla_activity1_household_watt_meter] to print or download.

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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 link
  • 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.)

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://internal.clarkson.edu/highschool/k12/project/energysystems.html.

Copyright

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

Contributors

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

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: October 16, 2021

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