Water Bender

A thin stream of water can be easily bent using a plastic comb or ruler which was previously rubbed with wool. This demonstrates the attractive forces between unlike charges.

Materials

  1. Plastic ruler
  2. Wool
  3. Water from a tap

Procedure

  1. Turn on the faucet for the thinnest stream of water with a consistent flow.
  2. Rub the plastic ruler with the wool.
  3. Place the part of the ruler which was rubbed near the stream of water without touching.

Science Explained

Water molecules are polar in nature, which means that one side (where the oxygen atoms are) is more negative while another side (where the hydrogen atom is) is more positive. When wool is rubbed with plastic, it deposits electrons on the ruler.

The electrons will remain on the plastic as it is a poor conductor of electricity. When placed near the stream of water, the water molecules reorientate themselves such that the positive pole of each molecule is now nearer to the ruler than the negative pole.

The resulting attractive forces are stronger than the repulsive forces as the forces between charges decrease when the distance apart increases.

Electromagnet

Materials

  1. Insulated wire (about 1 m in length)
  2. Iron nail (at least 5 cm in length)
  3. 1.5 V battery
  4. Adhesive tape
  5. Small metal paper clip

Procedure

  1. Test that the iron nail is not already magnetised by trying to pick up the metal paper clip with it.
  2. Strip the two ends of the wire off its insulation. Leave about 1 cm bare on each end.
  3. Coil the wire around the iron nail, pushing each coil tightly together, to make a solenoid. Make sure you leave about 5 cm free at each end of the wire in order to connect the battery to the solenoid.
  4. If there is excess wire, make a second layer of coils around the first layer.
  5. Connect the ends of the wire to the terminals of the battery.
  6. Test the solenoid now by picking up the paper clip.