Water has a skin-like covering formed by the way water molecules attract one another. This attraction is called surface tension. Objects such as needles and pins float effortlessly on this invisible skin. Needles and pins are also easily magnetized. Perhaps we can combine these characteristics.
Things Required:
A dozen sewing needles or pins
Magnet
Non-metal bowl
Water
Metal paper clip
Directions:
Magnetize about a dozen needles by stroking a permanent magnet along their length. Remember to stroke in only one direction.
Fill a bowl three-fourths full with water. Put a bend in a paper clip, forming a right angle between its two loops. Use this paper clip as a “cradle” to lower needles onto the surface of the water.
Place several needles on the surface of the water. Observe how their ends react to each other. What causes some of the needles to attract and others to repel?
Take a look at the shapes shown here. Can you steer the needles into the patterns below? Good luck.
This Is What Happens:
There are two major concepts at work here. The first is surface tension, which is formed from attractive forces between neighbouring water molecules. The second concept is magnetism. As you have learnt, like poles repel, while unlike poles attract. In order for needles to align end-to-end, the adjoining ends must have opposite charges. Once they are positioned correctly, the magnetic force helps keep their shape.
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