Lesson 3 of 3
Objective: SWBAT demonstrate that distance effects strength of electric forces as they experiment with static electricity.
Static means not moving. But when we experience static electricity it is because charges have moved from one item to another. Students have experienced the movement of current in electrical circuits.
In electrical circuits charges are moving all the time. Therefore static electricity is called static since the charges are mostly stationary. This lesson helps clarify the terminology along with supporting the standard MS-PS2-3 Ask questions about data to determine the factors that affect the strength and direction of electric forces.
Students will evaluate the strength of static electricity by experimenting with various materials to changes the charges present (MS-PS2-3 Ask questions about data to determine the factors that affect the strength of electric and magnetic forces.).
Students select from various materials to create charges that attract and repel as they play electron tether ball and attempt to guide a section of a plastic shopping bag across the room (SP3 Planning and Carrying Out Investigations).
Accumulating a wide variety of materials for students to use as they create static electricity helps to facilitate exploration and fun as they discover how to change the charge through electron movement. A suggested materials list can be found in the resources section.
In this lesson, students will be accessing an online simulation from PhET Simulations developed by the University of Colorado, Boulder. In this short video, I explain the rationale for using these simulations in my classroom.
Students in Action
Today is a perfect day to experiment with static electricity. We have had below normal temperatures for days, the heat has been on, the humidity is very low and just using a comb makes my hair stand on end.
Most of my students have had experiences with static electricity. They have stuck a balloon to the wall after rubbing it on their head and maybe they might have deliberately shuffled their feet to shock a sibling!
Okay, so we understand that like charges repel and unlike charges attract. We review the exchange of electrons that make this attraction / repulsion happen.
We recall that magnets act at a distance to attract and repel. When you bring opposite poles of the magnet close together the two magnets snap together. When you bring opposite poles of the magnet close together the two magnets move away from each other.
Next students access the PhET Static Electricity Simulation.
As I present student challenges, I ask them to make a mental note of the charges represented by the positive and negative signs. Students are expected to reference the charges in their response.
Students are challenged to make the balloon stick to the sweater. They can rub the balloon on the sweater. Then pull the balloon towards the wall but do not touch the wall. They balloon will move towards the sweater. Why are they attracted? What do you observe about the charges? The balloon takes negative charges from the sweater. The sweater retains positive charges so the opposite charges attract.
Next challenge, the students try to make the two balloon stick to the sweater. They can rub both balloons against the sweater, then pull the balloons towards the wall but not all the way to the wall and they will move toward the sweater. Why are they attracted? What do you observe about the charges? The sweater has a positive charge and the balloons have a negative charge.
Finally, can students make the balloons move apart. They can rub both the balloons on the sweater, move the balloons away from the sweater so they no longer stick to the sweater and the balloons will repel. Why did they repel? What do you observe about the charges? The balloon charges are the same.
Can we do the same with static electricity? Can the forces attract and repel at a distance?
Let's try playing tether ball with static electricity. Students make a tether ball by covering a dowel rod with foil and standing it in a small bit of clay. Next they use thread to attach the ball. I have provide small pieces of Mylar to represent the ball. Mylar is s good material to use because it has a thin coat of aluminum which is a conductor. It is easy to charge and discharge electrons. Students discover how using a balloon and various materials to create attraction of the tethered ball to the balloon or by repelling the tethered ball to the balloon, students attempt to wind the ball around the dowel rod. Just as the game is played on the playground.
Finally I challenge students to use a balloon to make a strip of plastic from a shopping bag repel and travel with the balloon as they walk.
This video shows a student successfully completing this final challenge. The student was able to accomplish the challenge by rubbing both the balloon and the shopping bag strip on his shirt so they had the same charges and repelled. One success lead to other students asking questions and duplicating results.
Connecting the Learning
There are no student notes or write-ups for this lesson. It was simply an exploration day. One learning goal for my students is that they always ask questions and seek answers even if there is no accountability in the form of a lesson write-up.
We do take a moment to talk about the definition of static electricity. Static, of course, means stationary. Did your observations indicate that the charges were stationary? No, in fact the goal was to move charges from one material to another.
Remember how the current moved in the PhET Magnets and Electromagnets simulation we visited in the Electromagnets lesson? What did you notice about the current? The current moved constantly as long as the circuit was connected.
What we observed in the Electromagnet lesson was current electricity. It moves constantly. Static electricity is mostly stationary. It does not have movement unless it is created by rubbing two materials together to cause the movement of charges. Static electricity gets its name because it is mostly stationary unlike current electricity.