## At Home: Practical activities

Practical Activity for 11-14 14-16 16-19

The activities in this collection are designed for remote teaching. Making use of equipment that can be found in the home, each activity here includes teacher notes and student instructions.

These will be added to regularly.

Expansion of the Universe
Earth and Space

## Elastic band universe

Remote teaching support for 14-16 16-19

In this activity students build a model universe using washers and elastic bands. You can use it to introduce Hubble’s law.

#### Equipment

Each student will need:

• 6 assorted washers (or paper clips)
• 5 elastic bands of the same thickness (and ideally of different lengths)
• Small sticker to indicate ‘home’
• Ruler or tape measure
• Graph paper (or laptop with Microsoft Excel or similar)
• Sticky tape
• A copy of the student instructions

#### Teaching notes

By following instructions on their activity sheet students should build a one-dimensional model of a universe. After expanding it to double its initial length they will need to stick the washers at the end of the chain to the table/floor to measure distances.

When they plot a change in distance against distance graph they should find that it is a straight line. Repeating with a different washer as the home galaxy reveals that the gradient of the graph is the same irrespective of which washer they consider to be ‘home’. Like real galaxies, the galaxies in the model seem to move away from home, but home is not the centre of the expansion. Observers in all galaxies will see the galaxies move away from them with a speed that is proportional to their distance from their galaxy. This is known as Hubble’s law.

 Model Universe The washers do not expand Galaxies do not expand (they are gravitationally bound) The elastic bands expand, carrying washers with them Space between the galaxies expands, carrying galaxies with it

#### Learning outcome

Students explain why observers in all galaxies see the galaxies move away from them with a speed that is proportional to their distance.

With thanks to the Perimeter Institute of Theoretical Physics for permission to adapt their activity

Charge
Electricity and Magnetism

## Attracting can

Practical Activity for 11-14

In this class activity, students see that after it’s rubbed against your clothes a balloon will attract a drinks can and make it roll. You can use it to introduce why charged objects exert forces on uncharged objects.

#### Equipment

Each student will need:

• Empty aluminium soft drink can
• Rubber balloon
• Cloth or woollen clothing

#### Procedure

1. Inflate the balloon and tie its neck.
2. Place the empty can on its side on a flat surface.
3. Hold the balloon close to the can. They should see that nothing happens because the balloon is initially uncharged.
4. Rub the balloon on their clothing or a piece of cloth so that it becomes charged.
5. Bring the balloon close to the can. They should see the can start to move towards the balloon.
6. Move the balloon gradually away from the can so that the can rolls along.

#### Discussion prompts

• After it’s been rubbed, the balloon attracts the can. Have you seen this sort of thing before?
• How can you tell that the forces on the aluminium can are unbalanced?
• How do you think the balloon creates a force on the can?

#### Teaching notes

Charged objects attracting other objects may be familiar from, for example, a comb attracting hair. You could rub the balloon and show that it also attracts a student’s hair. To help them visualise charging processes, introduce electrons as negatively charged particles that move between the materials.

The balloon becomes charged when it’s rubbed because it’s made of a material that attracts electrons more strongly than the cloth. Electrons are transferred from the cloth to the balloon and so the balloon gains a negative charge overall. Explaining that the cloth is left with a positive charge will help students appreciate that charge is conserved, but there is no need to discuss atomic structure or the nature of the positive charge in the objects.

The charging process for the aluminium can is different. The two objects do not come into contact. Instead, electrons in the can are repelled by the balloon and so move to the part of the can furthest away. The back of the can becomes negatively charged and the front positive, but overall the can remains electrically neutral. The reason the aluminium can starts rolling is because the back of the can is further away and so the repulsive force on the back of the can is smaller than the attractive force on the front.

If students use the phrase ‘static electricity’, explain that it can be a misleading one. The charging process for the balloon involves the transfer of charge between cloth and balloon, and the process for the aluminium can involves charges moving within the can. The charging processes may be different, but in neither are the charges ‘static’.

#### Learning outcome

Students describe how an object made of an insulating material becomes charged when we rub it and also why it then attracts other objects.

This experiment was safety-checked in March 2020.

Sound Wave
Light Sound and Waves

## Whistling Waveforms

Remote teaching support for 11-14 14-16

In this activity, students download an oscilloscope app onto a laptop or phone to investigate pitch and loudness. You can use it to introduce waveforms of sounds.

#### Equipment

Each student will need:

#### Teaching notes

Students should start by watching the video as described on the student activity sheet before downloading an oscilloscope onto a laptop or phone. Soundcard Oscilloscope on a Windows laptop is ideal as it provides a large display for easy comparisons of wave traces. If your students do not have access to a laptop, alternative free apps for smartphones or tablets are suggested on the activity sheet. If you recommend a different one, make sure it has a pause function.

If students can’t whistle, they can ask another person at home to be their sound source. Alternatively, they could blow over bottles or use a musical instrument such as a guitar or a recorder. They should see that when the sound is louder the peaks of the waveform are bigger, and that when the pitch is higher the peaks are closer together.

#### Learning outcome

Students draw waveforms for sounds with different volumes and frequencies.

With thanks to Christian Zeitnitz for permission to use Soundcard Oscilloscope