Has anyone heard of magnetic poles? A magnet has two poles: North and South. If you put two South poles near each other, they will repel each other; if you put two North poles together they will repel each other; if you put a North pole near a South pole, they will attract each other.
Give out coloured magnets and let the children try this out for themselves.
How strong are these magnets? Magnets exert their force over some distance, but what is the farthest distance we can put our magnets and still have them affect each other?
Hand out tape measures and encourage the children to experiment.
Give out Magnet Experiment sheets. The children should predict which items will be magnetic, then test their predictions and see if they were right.
Did you predict which things would be magnetic? Can you suggest some rules about what substances are magnetic and what substances aren’t?
Some metals are magnetic, more specifically iron and steel (an alloy of iron and carbon) are magnetic (also samarium and neodymium). In fact, the name for things that are attracted to magnets and are magnetized by touching magnets is Ferromagnetic, from Ferro meaning iron.
(If a material lines itself up with a magnetic field it is dangled in, it’s Paramagnetic.)
Paperclips are magnetic, so we’re going to use them to make a magnetic fishing game. Draw some fish and cut them out, then attach a paperclip to each one. Tie your ring magnet to a rope and a stick to make a fishing rod. See how many fish you can ‘catch’ in a minute, or time how long it takes you to catch them all.
Break for drink and snack
Does anyone know how to make a magnet?
Most of the electrons in an atom exist in pairs that spin in opposite directions, so the magnetic effect of one electron in a pair cancels out the effect of its partner. But if an atom has some unpaired electrons (iron atoms have four), these produce net magnetic fields that line up with one another and turn the whole atom into a mini magnet. When you put a paramagnetic material such as iron in a magnetic field, the electrons change their motion to produce a magnetic field that lines up with the field outside.
To make a magnet, we need to line up these unpaired electrons, and the magnetic fields throughout our object, to create one unified magnetic field.
There are three ways to do this.
The first way is with electricity. You may remember from our generators session that there is a connection between magnets, movement and electricity, if you have two of them, you can make the third. We used this theory to make electricity by spinning magnets set around a coil of wire. If I put electricity through a coil of wire around something iron, I can make an electromagnet.
Demonstrate making an electromagnet.
There are two other ways of making a magnet, and we’re going to test them both and see which is best.
First we’re going to try touching a magnet to a needle to magnetise the needle. We can check that our needles are magnetised using paperclips.
Then, we can use our magnetic needles to make simple compasses. If we put our needles on a bottle cap and float them in water, they will align themselves up with the Earth’s magnetic field and point North.
Let all the children have a go at making simple compasses.
There is one final way of making magnets. If we can line our metal up with the Earth’s magnetic field (which we can use our compasses to help us with!), and give it an encouraging tap – or twenty – then we should be able to magnetise our metal in that fashion.
Let all the children have a go and discuss the easiest method for magnetising metal.