To reinforce the concept that static electricity is a phenomenon that involves positive and negative charges.
This lesson is the third 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.
Before exploring the website, review with students some of the concepts leading up to this lesson.
Ask students these questions:
- What are atoms? (Atoms are some of the tiniest particles of any material or element. Atoms are the building blocks of matter.)
- What are the subatomic particles that make up an atom? (They are protons, electrons, and neutrons.)
- What kind of electrical charge do protons, electrons, and neutrons have? (Protons have a positive charge, electrons have a negative charge, and neutrons do not have any charge.)
- What often happens when you rub one object with another object? (When you rub one object with another, one of the objects will pick up some of the other object's electrons.)
- Explain what causes clothes to stick together when they come out of the dryer or a shock to occur after shuffling across the carpet and then touching a door handle. (The rubbing of clothes in a dryer or shoes on the carpet causes an imbalance of electrons. These electrons are then attracted to objects with the opposite charge.)
In this lesson, students will explore the Static Electricity section of the Science Made Simple website to learn more about the causes and effects of static electricity. Then, they will perform experiments demonstrating that opposite charges attract and like charges repel.
It may be useful to have students work together in pairs so they can help each other understand the facts and concepts in the online activity.
Distribute the More About Static Electricity student sheet. Ask students to answer the questions from the student sheet, as they explore the Static Electricity resource.
After students have had an opportunity to complete Part 1, lead a discussion of the questions they answered on the student sheets:
- What are three examples of static electricity? (Some examples might include: walking across a carpet and touching a metal door handle and pulling your hat off and having your hair stand on end.)
- When is there a positive charge? (A positive charge occurs when there is a shortage of electrons.)
- When is there a negative charge? (A negative charge occurs when there are too many electrons.)
- What role does friction play in static electricity? (Friction, or rubbing together of two objects, causes an imbalance of electrons by transferring electrons from one object to another.)
- When do objects attract each other? (Opposite charges attract. If one object has a negative charge and the other a positive charge, then they will be attracted to each other.)
- When do objects repel each other? (Like charges repel. If two objects both have a negative charge, then they will repel each other.)
Next, have students perform the activities as directed on Parts 2 and 3 of the student sheet. In Part 2, students will conduct the activity called Opposite Charges Attract. This is a simple demonstration of the effect of static electricity when objects with opposite charges attract each other using an inflated balloon, a few small pieces of paper, and wool.
After students have conducted the activity and recorded their answers to the questions, discuss with the class how the activity shows that opposite charges attract. Students should be able to explain that the paper is attracted to the balloon because the balloon has a negative charge and the paper has a positive charge. Thus, the opposite charges attract each other.
In Part 3, the Similar Charges Repel activity, students conduct another activity to demonstrate the effect of static electricity when objects with the same charge repel each other. Using two plastic combs, a piece of cotton string, and a piece of wool, students will charge two plastic combs and see what happens when the two combs come together.
After students have conducted the activity and recorded their answers, discuss with the class how the activity shows that similar charges repel. Students should be able to explain that both combs have an excess of electrons that was created by rubbing them on the wool. The suspended comb rotates away from the one in your hand because they both have the same charge.
To assess students' understanding, ask them to perform an experiment:
Supply each student with a plastic comb and several small pieces of paper. Ask students to find a way to use the comb to pick up the pieces of paper without touching them.
After students have completed their experiment, ask them to write down the steps they used to perform the experiment and whether the experiment worked. Also, ask students to write a brief explanation of what causes static electricity.
To perform the experiment, students should rub the comb against a wool object or another object that easily gives up its electrons. When the comb is rubbed, it becomes negatively charged with an excess of electrons. When the comb is placed close to the paper, the positive charges from the paper are attracted to the negative charges from the comb.
Students should be able to explain that static electricity is created when an object gives up or gains electrons.
Continue exploring these concepts with the next Science NetLinks lesson in this series, Static Electricity 4: Static Electricity and Lightning.
The following 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 an 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.