Science Club – Nuclear Power and Generators

Nuclear Power and Generators.
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Arrival Craft

Make paper windmills.

Intro.

You can make your windmill go round and round by blowing it. But you could also make it go round by holding it over the top of a boiling kettle. [demonstrate] You should never play with kettles, though, ask an adult to help you if you need to use one for an experiment. Today we are going to look at how power stations work – particularly nuclear power stations. Does anyone know what power stations are for?

Most power stations use generators to make electricity. A generator takes a round and round movement and turns it into electricity. In nuclear power stations the round and round movement comes from steam, just like the kettle I used to make my windmill spin. You can turn round and round movements into electricity by using magnets. Faraday’s Law tells us that when you move a magnet inside a coil of wire you create an electric current. I can demonstrate this with a multimeter, if I move the magnet in and out of the coil of wire, the number on the screen shows that I create a current. A generator, however, has a big magnet around the edge and a coil that spins very fast inside it. I’ve got some simple models here. If you spin the axles very fast the LEDs will light up, showing that you have made electricity flow. To make the axles spin very fast, you need to wrap some string around tightly then pull it away hard. [demonstrate, then give out motors so the children can have a go.]
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You do need to be patient with this experiment. We found that some attempts didn’t quite work, but after a few goes all the children managed to succeed at least once.

Individual Task

This week we are focussing on Nuclear Power stations.In power stations steam spin turbines that spin generators to generate electricity. Nuclear power stations use nuclear fission to heat water and make steam.

Some atoms are radioactive.

As we have mentioned before, atoms are made up of protons, neutrons and electrons. Every element contains these same basic ingredients, but different amounts of these ingredients forms different elements.

If you have lots of protons and lots of electrons you end up with a less stable element.

It’s sort of like this. If I pour a little bit of sand, it makes a neat pile, but if I keep pouring and put lots of sand grains in my pile, I end up with an unstable pile and grains start to tumble off.

Elements with lots of protons and electrons are unstable, they have a tendency to break apart and we call this being radioactive. When parts of the Uranium atom break away, you end up with different elements and every break releases energy in the form of heat. It’s that heat that is used to boil the water.

Uranium is a radioactive element. It has 92 Protons and 92 Electrons and 143 or 146 Neutrons. That’s a lot!

Now, when I poured the sand, I didn’t know how the big pile was going to collapse, or exactly when it would happen. And it’s like that with Uranium. We don’t know when any single Uranium atom is going to decay. If we have enough atoms, however, we can make a pretty good guess as to how long they will take to decay. We’re going to demonstrate this with some M&Ms. [give out M&M experiment sheets.]

NuclearPowerandGenerators

Break for drink and snack and put away the tables.

Second Half

When we did our M&M’s experiment, all the sweets fell independently. But that’s not exactly what happens in a nuclear reactor. Inside a nuclear reactor something called a chain reaction takes place. When a uranium atom decays, it breaks down into fission products and loose neutrons. These loose neutrons hit other uranium atoms, causing them to decay, emitting more loose neutrons, which hit more uranium atoms and so on and so on.

The idea of a chain reaction is that once you start it off, it just keeps going by itself. We’re going to have a go at setting up some chain reactions with lollipop sticks.
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Though there are plenty of people online who can do this, we found it very tricky!

Luckily, I also took along some packets of dominoes and the children had a lot of fun making chain reactions with those!

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Pneumatics at Science Club

Pneumatics.
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Arrival Craft: Popagami animals.

These are a lot of fun. They are available in packs if various sizes. You can even download free templates online to have a go.
You fold a box with ears, and inflate it into a little animal head.
They’re very cute when complete. You can see a mouse, a leopard and a horse in the centre of the photo at the top of this page.
We used this to talk about the force of air and how though you can easily move your hand through air, if you put air under pressure it can push up the paper.

Introduction: Can you think of anything that is moved by the power of air? Most of the time air doesn’t seem very strong, we move through it without giving it much thought. But air does have some strength and that can be used in lots of different ways.

The first thing we’re going to look at is putting air under pressure and then releasing it suddenly, when we release the pressure and give the air a way out, it will rush out very fast.

If I inflate this balloon and then let go without tying the end, what will it do? What will happen if I attach the balloon to something else before I let go? We can use the rush of air to push something else along, not just the balloon. If I attach a balloon to a straw on a string, then the balloon will rush down the string.

 

Individual Task: Balloon cars use exactly the same principle, if we attach a balloon to a simple car model, we can make it move. Hand out bottle tops for wheels, blue tac, skewers and straws for axles, cardboard for car bodies, balloons for power, and lots of sellotape! All the children (some with parents’ help) can make balloon powered cars.
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Break for drink and snack.

 

Gather together: We can also use the power of air in a more controlled fashion, if, rather than letting the air escape, we use a contained system and keep the air trapped.

If I have two syringes attached to a length of tubing, air cannot get in or out. If I push one syringe, the air will push up the opposite syringe. Demonstrate. This is called pneumatics.

You don’t have to filled the syringes and tubing with air. You can fill them with liquid. If you do that, it’s called hydraulics. I’m going to use water though hydraulic machinery is more likely to use oil, to avoid rust. We’re going to set up one set of syringes full of air and one set full of water, and use them both to lift a small weight. Watch carefully and see if you can see any differences between them.

The water compresses less than the air, because water is a liquid and air is a gas, so the water set moves more quickly. Hydraulics are more likely to be used in heavy machinery.

 

Second Activity: We’re going to make biting monsters powered by pneumatics. Give out tech card pieces and instruction sheets, and card for decoration. All the children can make their own biting monster.
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Seeing

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Arrival Craft:
Making thaumatropes.

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These are simple toys: a card disc on a stick with a picture drawn on each side. When you twist the stick in your hands, the two pictures appear to merge into one.
Common pictures are: a bird on one side and a cage on the other, a cat on one side and a mouse on the other, a fish on one side and a bowl on the other, or two faces which appear to kiss when the stick is turned.
The ‘magic’ works because of persistence of vision. Your eye continues to see the first picture for a couple of milliseconds, so when the second picture appears, you seem to see both at the same time.

Individual Task:
Making zoetropes.

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These use the same principal, but instead of two pictures merging, a strip of pictures merge together giving the illusion of smooth movement.
We made ours by cutting a cross in the centre of a paper plate, and sellotaping a marble there. This allowed the plate to spin freely and fast.
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Next we used black card to make a wall around the edge with slits cut out to look through. Ideally, these slits should be equal distances apart, but the effect seems to work pretty well even if your cuts aren’t exactly equidistant.
Finally we made strips of white paper to fit inside and drew cartoons on them. I made a juggler, the children made faces that changed expression, bouncing balls, and people jumping or skipping.
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Break for drink and a snack.
Second part:
We talked about eyes and I showed the children a big paper picture of an eye, which they stuck post it labels on.
Then we had a go at dissecting eyes.
In small groups of three and four, the children cut open an eye and tried to identify the pupil, the iris, the cornea and the lens.

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I bought the eyes from Samples for Schools. They arrive frozen.