What you Need
What to do
This works best on a dry day.
Set the tap running gently so that it has a stream of water coming out. Move the inflated balloon near to the stream of water.
Rub the balloon on your hair.
Now move the balloon near the stream of water.
What may happen
You should find that the uncharged balloon doesn't affect the stream of water but once you have rubbed it on your head the water is attracted, and attracted more the closer you move the balloon.
Why does it happen?
When you rub the balloon you touch the balloon to your hairs. when this happens a few electrons are transferred from the hair to the balloon. Rubbing repeats this millions of times, leaving the balloon charged.
The water starts off neutral, with the same amount of positive and negative charges. When you bring the charged balloon near to the water it pushes electrons away, leaving a positively charged area which is attracted to the balloon.
A similar effect is used in spray painting, the spray is charged in one direction and the object to be painted is charged the other way, so the paint is attracted to the object, and can even paint the back.