May the Forces be With You – Lesson 6 – Electrostatic Forces

Students will:

• explain that when an object gains or loses electrons it becomes negatively or positively charged and that the electric (electrostatic) force between objects with opposite charges attract and objects with like charges repel.
• describe electrostatic phenomena and technologies.

• To represent positive and negative charges: different coloured plasticine (alternative Blue tack, Playdough) and short lengths of pipe cleaner.
• Ready tables with materials for the activities
• It is advised that teachers test each of the suggested activities before conducting the lesson.
• Internet access will be required for watching videos.
• Access to a water tap

This lesson requires the following equipment:

• Whiteboard
• Balloons
• String to tie balloons to
• Tissue paper
• Scissors
• Sticky tape
• Plastic ruler or comb
• Empty soda cans
• Vinyl discs
• Cloth (woollen is best)
• PVC pipe (about 40 cm)
• Glass stick (optional)
• Electroscope (optional)
• Access to a tap and sink

If you are choosing to do the paper plate atom in the introduction then you also need:

• Paper Plates
• Pipe Cleaners
• Blue tack of at least two different colours

We learnt about forces in the last three lessons. Ask students to give some examples of forces.

Then introduce the lesson 6 learning intentions from the May the Forces be with You Lesson 6 PowerPoint.

In this activity we are reusing the paper plate atom activity from the Year 3 Atom Frenzy Module 1. We are doing this as a reminder and recommend that it could be done in groups to save time and resources. If your students have not done the activity in Year 3, you may want to do the activity in full. 

Introduce types of charges using two different coloured plasticine balls, black for negative and red for positive.

Review the structure of atom:

• Protons are positively charged, and neutrons have no charge. They are located in a miniscule ball in the centre of the atom.
• Electrons are negatively charged and are in a ‘fuzzy ball’ called the electron cloud that surrounds the nucleus.

Collect a paper plate, some red and blue plasticine, some pieces of pipe cleaner.

Working in your group, make a model carbon atom. Remember, carbon has 6 protons, 6 neutrons and 6 electrons.

• Make tiny red and blue plasticine balls to make a nucleus.
• Use Blutack to stick the electrons in the electron cloud.

Explain that the different charges attract each other, while the same charges repel each other. The idea of today’s activities is that you will see this attraction and repulsion at work.

First, we must learn what happens when electrons are gained or lost.

• Some of the electrons are held weakly and can transfer to other atoms.
• When this happens, each atom will either become negative or positive.
  • which ones become negative? (gain an extra electron)
  • which ones become positive? (lose an electron so have one extra proton)
• The negatively charged electrons are attracted to the positive nucleus.

Use the combination of charged balls to demonstrate negatively charged objects, positively charged objects and electrically neutral objects.

Teacher demonstrates the balloon and light plastic strip ‘electric flier’:

• Rub the inflated balloon with a piece of cloth for about 30 seconds
• Rub the flattened strip of plastic bag with the same cloth for about 30 seconds
• Hang the flat strip of plastic over a tightly strung length of nylon fishing line.
• Bring the charged balloon under and from the side of the charged strip of plastic.
• Observe what happens
• Give several children a turn, even set up 4 or 5 plastic strips on the stretched fishing line across the classroom so children can work in groups.

Watch the first half of the video for a demonstration of this activity. Then discuss this phenomenon with children through Predict, Observe, Explain.

Point out that there is no direct contact between the two objects. The force is operating over a distance. Note: Some of the students may already be aware of electrostatic forces.

Explain that when we rub the balloon and the piece of plastic bag, electrons are transferred from the cloth to the balloon and the plastic bag, just like in our ‘paper plate’ model atoms.

This caused extra electrons or negative charges to build up on both the balloon and the piece of plastic bag.

An alternative is to cut the plastic bags into strips to make plastic loops. Charge the balloon and the plastic bag loop and attempt to get the loop to hover over the top of the charged balloon. This takes quite a deal of practice to perfect.

The charges cause a force between the balloon and the plastic strip. This electric force balances the weight force.

The 2½-minute YouTube video Static Flyer Science Experiment by LAB 360 provides a concise explanation of the activity.

Watch the second half of this video for an explanation of this activity. 

Working in groups, students explore static electricity forces through a range of activities. Allocate two activities to each group.

They then use the Predict, Observe, Explain headings to report to the class.

Rotation 1: Ghost dancing

Children play with charged balloons and small pieces of tissue paper. Note that there is a video showing this activity here.

First cut out several tissue paper ghost shapes and draw a face with a marker. Different types of paper may be used for comparison.

• Students place their ghosts on their flat desk.
• Blow up and tie the balloon.
• Bring the balloon close to the paper ghosts.
• Then rub the balloon back and forward with the cloth.
• The balloon will gain static charge.

If students slowly bring the balloon near the ghost, and the ghost begins to rise toward the balloon and float right up to the balloon.

Prepare their report to the class:

• Predict: What you think might happen?
• Observe: What do you see happen? The paper ghosts floated up to and stuck on the balloon
• Explain: Explain what happened. (Before we rubbed the balloon it did not affect the paper ghosts. After we rubbed the balloon it attracted the paper ghosts and they stuck on the balloon because of an electrical force of attraction between the pieces of paper and the charged balloon)

For fun, try using the PVC pipe instead of the balloon.

• Which worked best?

Rotation 2: Rolling cans competition

Place an empty aluminium can on its side on the desk.

Blow-up and tie your balloon and before you rub it with a cloth bring it close to the empty can. What do you observe?

Then rub the balloon for about 30 seconds on a piece of cloth or on your hair.

One student brings the balloon close to the can without touching it to make it roll in one direction. Another student does the same on the other side, making it roll in the other direction.  The can will start to roll towards the balloons. Students can control how far the can rolls with charged balloons or compete against each other to see who can roll the can the fastest.

In this activity two students investigate the balancing of forces (See lesson 3) by drawing arrows to show the forces and how they combine.

Prepare a brief report to explain why the cans roll using the three headings: Predict, Observe and Explain.

Rotation 3: Water deflection

Provide access to a water tap.

Turn on the tap. How does the water flow from it? (observe the water flows in a stream straight down from the tap to the sink)

• Now slowly turn the water off until you have a very thin stream of water.
• One-at-a-time, rub a piece of polystyrene (cup or foam block), PVC pipe, blown-up balloon and a plastic ruler with a piece of cloth.
• Slowly bring each object close to the flowing water without letting it get wet.
• Write down your observation for each object.

Discuss the results in your group and try to explain why this happened.

Prepare a brief report to explain why the stream of water bent towards the charged object. Use the three headings: Predict, Observe and Explain.

Rotation 4: Dancing beanbag balls

Place a small handful of bean bag balls (expanded polystyrene balls) into a sealable sandwich bag.

• Shake these around.
• What do you observe?

Discuss the results in your group and try to explain why this happened.

Prepare a brief report to explain why the bean bag balls jumped around. Use the three headings: Predict, Observe and Explain.

Now we will see this in action when masses such as large heavy balls are added to spacetime.

Randomly select five of the group reporters to form a panel at the front of the class.

Ask each reporter to report their findings

• Predict: Why did . . . . . . . . happen?
• Observe: We saw . . . . . . . . . . . . . .
• Explain: This happened because . . . . . . . . . .

The presenter of each group should take part in ‘a science conference’ talking about the experiment they conducted.

Lead a discussion through the questioning: What we did? What we saw happen? Why did this happen?

Use scienctific language: “Experiments”, “Conclusion” and whiteboard for pictures. Through drama, students practice using scientific vocabulary such as: ‘electron’, ‘proton’, ‘charge’, ‘electricity’, ‘electrostatic force’, and ‘balanced forces’.

Finish off the lesson with the role play: Electron feels a force.

This part of the lesson could be conducted in a Drama lesson.

In this lesson we learnt about charges, static electricity, and electrostatic force. We also understand what lightning is and how electrostatics can be used by living organisms and in technology.

The 3-minute PBS video Static Electricity: Snap, Crackle, Jump provides an excellent summary of what happens to electrons when objects are charged:

https://www.pbslearningmedia.org/resource/phy03.sci.phys.mfe.zsnap/static-electricity-snap-crackle-jump/

In the next lesson we will learn about electrical forces involving moving electrons.

There are a range of activities that could be set up as a ‘semi-permanent’ display in a corner, side shelf or separate discovery centre table in the classroom. Students access the activities and displays during ‘free’ time – if they finish a task early, during a break, after school etc.

The discovery centre has displays, charts and access to YouTube videos and provides examples of how static electricity affects us every day through a range of exhibits and activities.

Explore these during the remainder of this topic when you get some free time if you finish a task early or during a break.

Atom: Building blocks of all matter.

Nucleus: The tiny central core of an atom.

Protons: Tiny positively electrically charged particles in the nucleus.

Neutrons: Tiny particles in the nucleus which have no charge.

Electron: Tiny negatively electrically charged particles that surround the nucleus.

Electron cloud: Ball or spherically shaped region around the nucleus where the electrons are found.

Electric/Electrical forces: Forces caused by electric charges.

Electrostatic forces: Forces between charges that are not moving.

Positive charge: The charge on a proton.

Negative charge: The charge on an electron.

Charged object: Something that has more protons than electrons is positively charged and something with more electrons than protons is negatively charged.

Neutral: No charge, the number of positive and negative charges balance out.

Attract: To pull together.

Repel: To push apart.