Jaimee, of Balclutha Primary School, asks :-
Why do magnets stick on the fridge?
Richard Blakie, an electrical engineer at the University of Canterbury, responded.
Magnets stick to the fridge door because, underneath the paint, the door is made of steel.
Magnets are attracted to certain metals, and if the attraction is strong enough they can hold on even when upside down. If you've played with magnets you might have seen that two magnets either repel each other (North pole to North pole or South pole to South pole) or attract each other (North pole to South pole). So why does a magnet always stick to the fridge door, no matter which way around it is? If the fridge door was a magnet then sometimes a magnet would be attracted and stick, and some times it would be repelled and fall off. Well, when a magnet comes close to the door it makes some of the metal into a magnet - if the North pole of the magnet is closest to the door then the surface of the door becomes a South pole and if the South pole of the magnet is closest to the door then the surface of the door becomes a North pole. This means that a magnet will always be attracted to the door.
Not all metals are the same, and not all attract magnets in this way. Metals with iron in them - like the steel of the fridge door - are magnetic, but metals like aluminium are not. Try sticking a magnet to an aluminium drink can and see what happens. What about a can of baked beans?