Strength of a Magnet
http://www.mocomi.com presents: Can magnets work through substances? REQUIREMENTS A magnet A glass container Water Safety Pin WHAT TO DO First, pour some water into the jug and drop the paper clip in it. Place the magnet on the outside of the jug, on the side of the paper-clip. WHAT HAPPENS When this is done, the paper clip follows the direction of the magnet until it is above the level of the water. WHY THIS HAPPENS This happens because the force of the magnet also works through the glass of the water. If the jug was made of iron or steel, the paper-clip would still come up but with a lesser intensity as the magnetic force would be absorbed by the sides of the jug.