Teaching Sequence

Work through this resource material in the following sequence:

20 minutes

Tune in: What will change?

20 minutes

Find out: Experiment time!

20 minutes

Reflection: What did we learn?

Tune in: What will change?

Step 1.

Begin by listing ways of generating electricity. Students might be able to list a range of renewable (wind turbines, solar power, hydropower) and non-renewable (fossil fuels such as coal and gas) sources.

But do students actually understand the processes that convert these energy sources into useable electricity?

Step 2.

Explain to students that today they are going to look at scale model of a hydropower dam. As they are conducting the experiment, ask students to keep in mind how they might implement this model as a renewable and sustainable energy source in the real world.

Find out: Experiment time!

Step 1.

Cut off the top of a large plastic bottle.

Step 2.

Make six holes around the base of the bottle with a pencil or knitting needle. Try to make sure these holes are as evenly spaced as possible.

Step 3.

Cut a straw into six even pieces and insert these into the holes in the bottle and secure them with some tape.

Step 4.

Make three holes (evenly spaced) at the top of the bottle and put a string through each of these holes. Tie the three strings to a fourth piece of string so that the bottle can hang.

Step 5.

Over the sink or outside, pour a jug of water in the bottle. When the water is pouring out of the straws, the bottle should spin around.

Step 6.

Now that students understand the basic principles of the experiment, have students write their predictions in the first section of the Student Worksheet, and then re-conduct the experiment with more or less holes in the bottom of the bottle.

Reflection: What did we learn?

Before we know why this experiment was important to the real world, we need to understand how electricity works.

When we talk about electricity, we are actually talking about the flow of electrons through a wire. Electrons are tiny negatively charged particles that are found in all atoms. When we move these electrons from one place to another, we create an electric current.

When we flick a switch for a lamp, the resulting light is what we can see of a current of electrons passing down a wire and across the filament.

One of the most common ways to create this current is via a device called a generator. In this device, a magnet spins. The magnetic field has two poles - north and south. These poles have opposite magnetic charges, meaning that the north pole attracts the south pole of another magnet, while repelling the north pole of another magnet.

When a magnet rotates, it creates a magnetic field around it. This magnetic field is like an invisible force that can affect things around it.

Also in the generator are many coils of wire. When we bring these coils close to the rotating magnet, the magnetic field of the magnet passes through the wire. This creates a flow of electrons in the wire, as the electrons are attracted to one pole of the magnet and repelled by the other pole via the magnetic field. This causes the electrons in the wires to flow in a certain direction, which we call an electric current.

The faster the magnet rotates, the stronger the magnetic field becomes, and the more electrons are induced to flow in the wire.

What does this have to do with our water experiment?

Well, the thing that makes the magnet rotate is called a turbine. The turbine is like a cog or a big fan attached to the magnet via a long shaft. When the turbine spins, the magnet spins.

Can you see how this is related to our experiment?

Commonly a turbine is caused to spin by burning coal or gas, causing water to heat into steam and rise through the turbine, making it spin.

However, if we have a source of kinetic energy, such as the wind or a flowing river, we can make the turbine turn forever, and without spending any resources.

So, if we can recreate our plastic bottle model on a huge scale - which is what hydro-electric dams are - then we can generate electricity for our homes!

How Can Water Generate Electricity?

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