SummaryThis hands-on activity explores the concept of static electricity. Students attract an O-shaped piece of cereal to a charged comb and watch the cereal jump away when it touches the comb. Students also observe Styrofoam pellets pulling towards a charged comb, then leaping back to the table.
Engineers consider static electricity when designing, manufacturing and packaging electronic circuit boards. If too much static electricity is present, the electrical components on the circuit board may malfunction and the circuit board may become inoperable. When fabricating circuit boards for computers and electronics, engineers wear special white suits called "bunny suits" and work in "clean rooms" to help protect the circuit boards from contaminants and static electricity.
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.
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.
- Ask questions to determine cause and effect relationships of electric or magnetic interactions between two objects not in contact with each other. (Grade 3) Details... View more aligned curriculum... Give feedback on this alignment... Thanks for your feedback!
- 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. (Grades 6 - 8) Details... View more aligned curriculum... Give feedback on this alignment... Thanks for your feedback!
- Draw a scaled picture graph and a scaled bar graph to represent a data set with several categories. Solve one- and two-step "how many more" and "how many less" problems using information presented in scaled bar graphs. (Grade 3) Details... View more aligned curriculum... Give feedback on this alignment... Thanks for your feedback!
After this activity, students should be able to:
- Describe static electricity and how it affects different objects.
- Observe different manifestations of the electrostatic force that occur as a result of the transfer of electric charge.
- Understand that engineers must consider static electricity when designing, manufacturing, and packaging electronic equipment like circuit boards.
Each group needs:
- 1 rubber or plastic comb (or a balloon)
- 1 12-inch piece of thread
- 1 piece of O-shaped cereal
- Long, dry hair or dry wool cloth
- A few Styrofoam packing pellets
- Scotch tape
- Counter top or table
- 2 Fun Things to Do with a Rubber Comb Worksheet
Ask the students if they have ever had a hat on during the winter, taken off the hat and had their hair stand up or crackle? (Answer: Some may say yes.) Ask students what is it that causes this to happen? (Answer: Static electricity.) Now, ask students if they have ever taken clothes out of the dryer and had them stick together? (Answer: Some may say yes.) See if any student has heard the crackle when you pull the clothes apart. Again, ask students what is it that causes this to happen? (Answer: This is also static electricity.) How is it possible that what causes your hair to stand up after taking off a winter hat is the same as what makes your clothes stick together in the clothes dryer?
Draw a diagram of a Bohr model (see Figure 1) on the board and explain that all ordinary matter (everything around them) is made of atoms. Make sure to point out that an atom has a positively-charged nucleus and negatively-charged electrons surrounding the nucleus. In the nucleus are protons, which have a positive charge, and neutrons, which have a neutral charge (neither positive nor negative).
[In-class demo] Ask for 12 volunteers. Have students create a human diagram of the Bohr model by setting up two chairs. Have two students walk in one direction around the first chair and two students around the second chair. This is the first shell of the atom. Next, have one student walk in the other direction around the first chair, and seven students walk around the second chair to represent the second shell of electrons. Explain to students that static electricity happens when the two atoms rub together and the single electron from the first atom is transferred to the seven-electron shell of the second atom.
Tell students that static electricity depends on the balance of charges in an atom. Believe it or not, an electron can move from one atom to another, creating electricity! Also, tell students that electrons (or charge) can move from one object to another by rubbing two objects together.
Ask if students have ever heard the "opposites attract" saying for magnets? Tell them that the same is true when it comes to charges in an atom. Explain that a positive and negative charge (opposites) pull toward each other. However, negative charges push away other negative charges and positive charges repel other positive charges. Tell students that the attraction and repulsion (pushing away) of charges is the basis of static electricity and that they will learn more about static electricity during the activity.
Engineers consider static electricity when designing, manufacturing and packaging electronic circuit boards. If too much static electricity is present, the electrical components on the circuit board may malfunction and the circuit board may become inoperable. When fabricating circuit boards for computers and electronics, workers wear special white suits called "bunny suits" and work in "clean rooms" to help protect the circuit boards from things like static electricity. These bunny suits prevent human skin and hair particles, as well as lint particles from entering the clean room, which can damage the circuit boards by conducting electricity between two spots on the board that should not be connected. Also, a bunny suit helps prevent static electricity in your body from sending unwanted electric charges to the circuit boards and damaging them.
Background - The Atom
Everything we see around us — all ordinary matter — is made of atoms. Every atom consists of negatively-charged electrons and a positively-charged center called a nucleus. The nucleus is made of positively-charged protons and neutral-charged (neither positively- nor negatively-charged) neutrons. In a simple model of an atom, known as a Bohr model (see Figure 1), it is assumed that the electrons are spinning around the nucleus of the atom on paths called orbitals. One can visualize this by thinking of satellites orbiting the Earth, or the moon orbiting around the Earth. The positive charges of the protons in the nucleus attract the negative charges of the electrons orbiting around the nucleus (opposites attract), maintaining the electrons' orbit. Charge is a fundamental quantity in electricity. The smallest amount of charge that is known to exist is carried by an electron and has a charge of -1.602 x 10-19 coulomb [C]. The other charge-carrying portion of the atom is the proton, which has a charge of +1.602 x 10-19 coulomb [C]. The unit used to measure charge is known as the Coulomb, named after French engineer and physicist Charles Coulomb.
Background - Static Electricity
In an atom, the protons and neutrons that make up the nucleus are held together very tightly and rarely does the nucleus experience a change. However, some of the electrons that are associated with the atom are loosely held to their orbital. These electrons, which typically reside in the outer orbits, can move from one atom to another. When an atom loses electrons, it has more positive particles than negative particles, which results in a positive net charge for the atom. An atom that acquires electrons has more negative particles than positive particles and, thus, has a negative net charge.
If the atoms in a material hold the electrons in the outer orbits tightly, the electrons are less likely to move to another atom. Such materials are known as insulators. Alternatively, materials whose atoms willingly give up and accept electrons are known as conductors. Conductors allow electrons to move through the material easily.
It is possible to transfer (or move) electrons from one material to another. One way to do this is by rubbing two objects together. The longer that two objects are rubbed together, the larger the quantity of electron movement from one object to the other, which results in a charge build up on each object. Static electricity occurs when there is an imbalance of positive charges and negative charges.
Positive and negative charges behave similarly to the north and south poles of a magnet: Opposite poles attract and like poles repel. In the case of charges, a positive and negative charge pull towards each other. Positive charges repel other positive charges, and negative charges push away other negative charges. Therefore, an object that has a positive or negative charge build up (net charge) attracts an object that is neutral. For instance, when you rub a balloon on your hair or a piece of wool cloth, the balloon acquires additional electrons. If you hold the balloon against a wall, the balloon sticks. This is because the negatively-charged electrons on the balloon push away the negatively-charged electrons in the wall (like charges repel) and attract the positive charges in the wall (opposites attract), causing the balloon to stick to the wall. Additionally, when an object with charge build-up attracts a neutral object, the electrons tend to move to areas where the electrical charge is positive until the atoms in both objects are neutral or balanced. When a large number of electrons move in an effort to balance the atoms, there is a chance of seeing a spark. This spark is a result of static electricity.
Before the Activity
- Gather the materials.
- Make copies of the Fun Things to Do with a Rubber Comb Worksheet.
- You may want to cut the thread in advance.
With the Students
- Suspend an O-shaped piece of cereal from a tabletop, using scotch tape and a piece of thread (see Figure 2).
- Next, take a comb (or balloon) and quickly rub it through your hair or on a piece of wool cloth. Note: For this entire activity, a blown-up and tied-off balloon may substitute for a rubber comb.
- Hold the comb near the cereal. The cereal should swing toward the comb (see Figure 1). Hold the comb still until the cereal touches the comb. Next, observe the cereal quickly move away from the comb
Ask students why the cereal was attracted to the comb, but then moved away once the cereal touched the comb? (Answer: The rubber comb attracted the loosely-bound electrons that were on the student's hair or the piece of wool. Once the comb attracted the electrons, it gained a negative charge. The cereal initially has a neutral charge; therefore, it is attracted to the comb because of its different charge distribution. However, when the cereal touches the comb, it gains some of the comb's negative charge, and the cereal's charge distribution becomes the same as that of the comb. Next, the two objects repel each other since they are now "like objects," and as a result, the cereal moves away.)
- Spread some Styrofoam pellets on the table.
- Rub the comb through your hair or against the wool cloth again. Next, move the comb close to the Styrofoam pellets. The pellets stick to the comb. After several seconds, the Styrofoam jumps back to the table. Discuss what was observed (similar to step 3).
- If time permits, extend the activity to include the math applications described in the Activity Extensions section.
- Ask students to refrain from throwing Styrofoam pellets or O-shaped cereal.
When rubbing the comb in hair, it works best if the hair is dry and clean. Otherwise, a piece of wool material works best.
Humidity dissipates charge, so this activity does not work as well on humid or rainy days.
Human Diagram: Ask for 12 volunteers. Have students create a human diagram of the Bohr model by setting up two chairs. Have two students walk in one direction around the first chair and two students around the second chair. This is the first shell of the atom. Next, have one student walk in the other direction around the first chair, and seven students walk around the second chair to represent the second shell of electrons. Explain to students that static electricity happens when the two atoms rub together and the single electron from the first atom is transferred to the seven-electron shell of the second atom.
Prediction: Have students predict the outcome of the activity before it is conducted. First, give an overview of the activity, then ask students the following question and have them write their answer on a piece of paper. Then, perform the activity.
- What do you think will happen if you rub the comb on your sweater and hold it by a piece of cereal?
Activity Embedded Assessment
Worksheet/Pairs Check: At the beginning of the activity, hand out the Fun Things to Do with a Rubber Comb Worksheet. Have students work individually or in pairs to complete the worksheet. Have students who work in pairs check each others' answers.
Student-Generated Questions: Have each student come up with one question of their own to ask the rest of the class. Be prepared to help some students form a question. Possible questions:
- What type of electricity attracted the cereal to the comb at first?
- Why did it repel quickly after it touched the comb?
- Do items with negative charges (more electrons) attract or repel other items with negative charges?
Question Races: Have each student group number off by threes or fours so that at least three groups have the same number. Ask a question and call a number. Each group with that number should send on student to run up to the board and write the answer for the question. Each student who gets it right earns their team a point.
- Give an example of static electricity.
- Who invented the light bulb? (Answer: Thomas Edison)
- What part of an atom can move to another atom? (Answer: Electron)
- How many electrons reside in the first orbital around the atom? (Answer: 2)
- How many electrons reside in the second orbital around the atom? (Answer: 2)
- How many electrons reside in the third orbital around the atom? (Answer: 6)
A good inquiry for this activity is to have students bring in different types of cereal from home. Have them predict how long the cereal will stay attracted to the comb. On a bar graph, they could graph the length of attraction vs. type of cereal.
Extend the activity to include the following math applications:
- Does the size of the comb or cereal make a difference? Try measuring diameters of different cereals or measuring the length of the comb. Test a hypothesis on whether size of the objects matters.
- How far can the cereal be made to move? Measure the distances at which you can place the comb and still get the cereal to move.
- Try timing the rubbing time of the comb and see if doubling the rubbing time makes the cereal move farther or faster.
ContributorsMonica Maxwell; Daria Kotys-Schwartz; Malinda Schaefer Zarske; Denise Carlson
Copyright© 2004 by Regents of the University of Colorado.
Supporting ProgramIntegrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.