GO IN DEPTH

Static Electricity 2: Introducing Static Electricity

Materials

Stuck-Up Balloon Activity

• balloon
• piece of fur or wool
• a blank space on a nearby wall

Dancing Balloon Activity

• 2 balloons
• 2 pieces of thread or lightweight string about 2 feet long (exact length is not critical)
• wool as in previous activity

Purpose

To introduce students to static electricity as a phenomenon that involves positive and negative charges.

Context

This lesson is the second of a four-part series on static electricity. These lessons are meant to help students understand that static electricity is a phenomenon that involves positive and negative charges.

An understanding of static electricity must begin with the concept that all matter is composed of atoms, and all atoms are composed of subatomic particles among which are the charged particles known as electrons and protons. Protons carry a positive charge (+), and electrons carry a negative charge (-). The number of electrons in an atom—ranging from one up to about 100—matches the number of charged particles, or protons, in the nucleus, and determines how the atom will link to other atoms to form molecules. Electrically neutral particles (neutrons) in the nucleus add to its mass but do not affect the number of electrons and so have almost no effect on the atom's links to other atoms (its chemical behavior).

To further understanding about static electricity, you should help your students to make connections between their day-to-day experiences with static electricity—such as lightning, receiving shocks after shuffling across a carpet, taking clothes that cling to each other out of the dryer, combing their hair in the wintertime—with the static activities conducted in the classroom. Ask them to try to describe and explain their everyday experiences with static in the terms they are learning: repel, attract, static charge, electron transfer. It is important that students grasp the concept that oppositely charged objects attract each other and like charged objects repel each other. It is less important that they are able to recall which materials tend to acquire negative or positive charges.

When two different materials come into close contact, for example, felt rubbing against a balloon or two air masses in a storm cloud, electrons may be transferred from one material to the other. When this happens, one material ends up with an excess of electrons and becomes negatively charged, while the other ends up with a deficiency of electrons and becomes positively charged. This accumulation of imbalanced charges on objects results in the phenomena we commonly refer to as static electricity.

When students first begin to understand atoms, they cannot confidently make the distinction between atoms and molecules. Students often get the idea that atoms somehow just fill matter up rather than the correct idea that the atoms are the matter. Middle-school students also have trouble with the idea that atoms are in continual motion. Coming to terms with these concepts is necessary for students to make sense of atomic theory and its explanatory power. (Benchmarks for Science Literacy, p. 75.)

In Static Electricity 1: Introducing Atoms, students are asked to review websites to learn about the atom's basic structure and the positive and negative charges of its subparticles. This lesson lays the groundwork for further study of static and current electricity by focusing on the idea of positive and negative charges at the atomic level. Due to the amount and complexity of the information related to this topic, students will gain an understanding of these concepts over time. It is important that they explore this topic in a variety of contexts.

Static Electricity 2: Introducing Static Electricity helps expand students’ concepts about atoms and how they relate to static electricity. In this lesson, students perform some simple experiments, creating static electricity to demonstrate how opposite charges attract each other and like charges repel each other. Then, students explore a website that further explains these concepts.

Static Electricity 3: More About Static Electricity helps expand students' concepts about atoms and how they relate to static electricity. In this lesson, students explore a website to investigate concepts related to static electricity. Then, students perform experiments in which they create static electricity and demonstrate how opposite charges attract each other and like charges repel each other.

Static Electricity 4: Static Electricity and Lightning introduces students to concepts about lightning and how they relate to static electricity. In this lesson, students explore a variety of websites to learn about lightning and then explain in their own words what causes lightning and how it is related to static electricity.

Motivation

Begin by discussing the following questions:

• Have you ever been shocked after walking on a carpet or putting on a sweater? Combing your hair? Getting out of a car with cloth seats? Can you explain what caused the shock?
• Describe your experiences playing with magnets. Have you noticed that sometimes two magnets will repel each other? What causes them to repel?
• Why do your clothes stick together when they come out of the dryer?
• Why do you sometimes get a shock on a cold day when you touch metal?
• What other experiences have you had with static electricity?

Now, have students perform some simple activities to reintroduce them to the concepts of static electricity that they may have covered in an earlier grade. Divide students into cooperative groups of two or three and instruct them to perform the Stuck-Up Balloon and Dancing Balloon experiments with their group. After each experiment, call the groups together to discuss their observations and conclusions.

After students have completed the Stuck-Up Balloon activity, say to them:

When you rub the balloon with wool, negatively charged particles called electrons are transferred from the wool to the balloon, giving the balloon an overall negative charge. When the charged balloon is brought near the wall, it repels some of the negatively charged electrons in that part of the wall (negative charges repel other negative charges, and positive charges repel other positive charges). Therefore, that part of the wall is left repelled. Then, the negatively charged balloon and the positively charged section of the wall are attracted to each other, and the balloon sticks. The charged balloon may be made to stick to a wide variety of objects (even a person) because of the charge it receives after being rubbed.

Now, have students do the Dancing Balloon activity. Once they have completed this activity, say to them:

When we rub the balloons with the wool, each of the balloons acquires a negative charge. Negatively charged particles called electrons are transferred from the wool to the balloons, giving the balloons an overall negative charge as in the Stuck-Up Balloon Activity. Because the two balloons have the same kind of charge, they repel each other.

Development

Begin this part of the lesson by having students explore resources on the Basics of Static Electricity, on the School for Champions website. Ask students to answer the questions on the Introducing Static Electricity student sheet as they explore the specific resources on the Basics of Static Electricity site. Students can use their notes during the class discussion.

After students have had an opportunity to review the website, lead a discussion of the questions they answered on their student sheets:

• What is the difference between electrons and protons? (Electrons have a negative charge and protons have a positive charge.)
• When does a piece of matter have a "charge?" (A piece of matter has a charge when it has more of one type of particle, either electrons or protons, than another.)
• What happens if two objects have the same charge? What happens if two objects have different charges? Can you think of an example of this? (Objects with the same charge will repel. Objects with different charges will attract each other.)
• What often happens when you rub one object with another object? Describe what happens using a specific example. (When you rub one object with another, one of the objects will pick up some of the other object's electrons.)
• What kinds of objects give up electrons easily? (Examples are hand, glass, hair.)
• What kinds of objects pick up electrons easily? (Examples are polyester, plastic, rubber.)

After the discussion, refer students to the Understanding What You've Learned section of the student sheet in which they are asked to explain in their own words what causes static electricity. Their explanation should include examples of static electricity in everyday life, as well as discuss the role of electrons and protons in static electricity.

Assessment

Assess students' understanding by how they have responded to the last part of the student sheet. Though answers will vary, students should generally be able to explain that since electrons and protons have different charges they are attracted to each other like magnets are attracted to metal objects. However, protons repel, or push away from other protons, and electrons push away from other electrons. These forces-attractions and repulsions-make static electricity. Students might also say that static electricity is created when two objects are rubbed together, causing an object to give up or gain electrons. This can happen by putting on a sweater, walking on a carpet, or getting out of a car. The imbalance of charges on objects results in static electricity.

You can also assess student understanding by having them draw a diagram illustrating the movement of electrons that occurs during static electricity.

Extensions

Follow this lesson with the next two lessons in the Static Electricity series:

These Internet resources can be used to further explore the topics related to static electricity:

• Activities to explore Static Electricity, on the Boston Museum of Science site, provides background information for the teacher and includes several experiments demonstrating static electricity.
• Static Electricity, part of Frankenstein's Lightning Laboratory on the Atoms Family site, is a static electricity experiment that uses a plastic comb, wool cloth, puffed rice, and a large plastic bag with tie.
• Other activities in Frankenstein's Lightning Laboratory include Electrical Safety and Fruity Electricity.