Build a Charge Detector

Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder Xochitl Zamora Thompson, Sabre Duren, Joe Friedrichsen, Daria Kotys-Schwartz, Malinda Schaefer Zarske, Denise Carlson
Type Category
Instructional Materials
Lesson/Lesson Plan , Graph , Activity
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



Students investigate the transfer of electric charge and electric force by building and using electroscopes.  They use the electroscopes they built, to make qualitative observations about the static electric charge between pairs of objects.  A separate activity has students graph sets of pre-given data, in order to determine the relationship between force and charge, and between force and distance, for pairs of charged objects.

Intended Audience

Educator and learner
Educational Level
  • Middle School
  • Grade 8
  • Grade 7
  • Grade 6
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

MS-PS2-5 Conduct an investigation and evaluate the experimental design to provide evidence that fields exist between objects exerting forces on each other even though the objects are not in contact.

Clarification Statement: Examples of this phenomenon could include the interactions of magnets, electrically-charged strips of tape, and electrically-charged pith balls. Examples of investigations could include first-hand experiences or simulations.

Assessment Boundary: Assessment is limited to electric and magnetic fields, and limited to qualitative evidence for the existence of fields.

This resource appears to be designed to build towards this performance expectation, though the resource developer has not explicitly stated so.

Comments about Including the Performance Expectation
This activity asks students to build and then use a tool, in order to detect the presence of static electric fields, and to qualitatively compare the strength of electric charges on various objects. The existence of fields is the reason why the electroscope works. The activity uses the word “charge” but does not use the vocabulary of “electric fields”. The teacher will need to discuss this, if the students have not already had a lesson about electric fields. It will be important for the teacher to ask students to explain why the electroscope works, before using it to test other pairs of objects. This will ensure that students understand that the electroscope is responding to an electric field between itself and another object. A good place for this questions/discussion would be between steps 9 and 10 of the given procedure. This information is laid out in the “Activity observations and explanations” section; it is not recommended that students read this, but rather that they construct and share their own explanations. The reading could be used for reinforcement later, for students who need it. (Note: the graphing activity in this lesson could be used in conjunction with other lessons to work toward standard MS-PS-2-3, “Ask questions about data to determine the factors that affect the strength of electric and magnetic forces”.)

Science and Engineering Practices

This resource appears to be designed to build towards this science and engineering practice, though the resource developer has not explicitly stated so.

Comments about Including the Science and Engineering Practice
Students use the electroscopes they built to examine the different charges on various pairs of materials. The lesson does not give students an overt purpose for doing this, but it is implied that the purpose is to test out the electroscopes they built, on a variety of charged and uncharged objects. Students are also asked to find out whether the amount of rubbing affects the amount of charge. One of the extension activities, in which students have access to other materials to make electroscopes of their own design, will be helpful in addressing the “test design solutions” portion of this practice. A teacher will also likely want to have students record their findings of not only the “balloon” test, but also for the students’ own tests with various objects, although this is not mentioned in the lesson plan. See the “Instructional Supports” section for ideas about recording findings. (Note: students will need to be familiar with the idea of the triboelectric series, in order to choose pairs of objects that do produce a charge. A chart of the series is included in the materials list, but there are no teacher or student instructions about using it.)

Disciplinary Core Ideas

This resource appears to be designed to build towards this disciplinary core idea, though the resource developer has not explicitly stated so.

Comments about Including the Disciplinary Core Idea
Although the word “fields” is not used in the lesson, the function of the electroscope is to show where electric fields are present.

Crosscutting Concepts

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
This concept is best addressed through the discussion of how an electroscope works, and by a teacher’s sharing the “Engineering Connection” background information with the class. The post-activity discussion questions also ask about the connection between structure and function of parts of the electroscope, although the exact words “structure” and “function” are not used.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This resource, although a bit vague in its wording, can be used to address the performance expectation. It also has connections to a scientific practice, disciplinary core ideas, and a cross-cutting concept. A teacher will need to emphasize these connections by ensuring students come into the activity with a knowledge of the concept of “fields”, discussing the workings of the electroscope, and clarifying the relationship between the electroscope activity and the graphing activity.

  • Instructional Supports: The students work with real world phenomena (static charge on objects, building tools), and a mathematical representation (graphs). The information is grade-appropriate. Students may be offered the opportunity to share, clarify, and revise their ideas if the teacher has them explain their ideas about how the electroscope works. The lesson includes troubleshooting tips, extensions and activity scaling sections, which offer ideas for differentiating the activities. Background information, or portions of it, can also be used as reinforcement of concepts for students. A teacher could also provide different methods for students to record the data from their electroscope tests, including narrative description, diagrams, and/or a chart to fill in about the objects chosen, amount of rubbing, distance of electroscope, and observation of electroscope. For some high-needs students, portions of the chart could be pre-filled by the teacher as an example.

  • Monitoring Student Progress: The lesson includes sections on pre-activity assessment, during-activity assessment, and post-activity assessment. These assessments are all heavy on the “one right answer” kind of question and could be strengthened by asking more open-ended questions that have students explain their thinking and/or use evidence to support their claims. A teacher might, for instance, ask students what happens to the strength of a force as charged objects are moved farther apart, and ask the students to provide evidence from their data from the two activities to support their claim. The pre-activity and during-activity questions are primarily about core ideas, while the post-activity questions relate strongly to the cross-cutting idea of structure and function. Using open-ended questions such as the one suggested above would strengthen the assessments’ connection to the Practice. The lesson provides answers to the assessment questions and an answer key for the graphs, but does not provide rubrics or scoring guides.

  • Quality of Technological Interactivity: This lesson does not include computer interactivity.