Forces and Interactions
Exploring magnets
Sort materials into magnetic and non-magnetic, find the poles of a magnet, and work out what happens when two magnets are brought together.
Bring a magnet near a handful of odds and ends and it sorts them for you. A few jump to it; the rest sit where they are. The ones it draws towards itself are made of magnetic materials — iron chief among them, and nickel and cobalt too. The ones it leaves alone are non-magnetic.
Poles come in twos
Scatter iron filings under a bar magnet and they crowd at the two ends, hardly any along the middle. Those two ends are the poles: North and South. Break the magnet in half and you do not get one pole each — you get two smaller magnets, each with a North and a South of its own.
Have a play
Along a bar magnet, the pull is strongest at some places and weakest at others.
Tap any part of the picture.
Worked example
You have two iron-colored bars. One is a magnet and one is a plain iron bar, and they look identical. How do you tell which is which?
Try attraction first, and notice it settles nothing: bring a known magnet's North pole to each bar in turn. Both are drawn to it.
A plain iron bar is a magnetic material, so it is pulled towards either pole. Attraction happens with both bars, so it cannot separate them.
Try it together
Now work out why a compass is of any use to a sailor.
The needle inside a compass is a small magnet, free to turn. Follow what that gets you.
1.A magnet hung so that it can turn freely comes to rest pointing along one particular line. Which two directions does that line join?
Have a go
Have a go on your own. Magnets that occur in nature, and that the earliest sailors' magnets were based on, have a name. What are they called?
Ready to practice?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.