Electrostatic touchscreen
Manipulate lightweight objects with an invisible force!
Safety
- Carefully review the general safety advice on the back of the box cover before starting the experiment.
Step-by-step instructions
When rubbed against the tissue, the straw becomes electrified and begins to interact with the foam balls. Once attracted to the straw, the balls become electrified themselves. Do not touch other objects with the straw—if you do, it will give them its charge!
Now see what happens if you electrify the Petri dish lid!
Curiously, the electrified lid can attract the foam balls, too. Wow! A simple touch removes the electrification from that area of the lid, so the balls have to escape to the areas that you have not yet touched.
Disposal
- Dispose of solid waste together with household garbage.
Scientific description
Everything that surrounds us consists of tiny particles. Some of them carry an electrical charge, which can be positive 
or negative 
. In particular, an electron carries a negative charge , and a proton carries a positive charge . Particles with like charges repel one another, while particles with opposite charges attract one another.
If an object carries an equal number of positive and negative charges, it is said to be electrically neutral. Most objects around us are neutral. However, when rubbed together, one object can take some electrons from another. This results in one object retaining more electrons than protons , and the other—vice versa. Objects in which the numbers of protons and electrons are imbalanced are said to be electrified.
How can you tell if an object is electrified? An electrified object will interact with the charged particles in a neighboring object. And if the latter is lightweight enough, your electrified object will be able to noticeably attract it.
For instance, as you rub the Petri dish lid 
against the cloth, electrons migrate from the cloth onto the lid. The lid now has an excessive negative charge. When you bring this lid close to the lightweight foam balls 
, the negatively-charged lid attracts the protons in each foam ball and simultaneously repels the electrons in them, which in turn causes the electrons in the foam balls to push away from the lid. The closer the charged objects are brought to each other, the stronger they interact, and finally, the foam balls stick to the lid.
Why do the balls fly apart 
when you touch 
the lid ? When you make physical contact with the lid , your finger collects electrons from the point of contact. Without its extra electrons , that area on the lid no longer attracts the foam balls .
