Question

Everyone knows this experiment: You mix salt and pepper and use a charged balloon to separate the pepper from the salt.

I never really understood how this works. In school (long time ago) we learned that unlike charges attract each other while like charges distract each other. In the experiment the negatively charged balloon attracts the pepper. Does this mean the pepper has a positive charge?

Why is pepper charged? How can I predict for given particle if the balloon will attract, distract or not interact with it?

Answer 1

A negatively charged balloon attracts pepper particles not necessarily because they have a positive charge, but due to the polarization and induced opposite charge on the pepper when near the balloon. To predict interactions, consider charge types and the propensity of materials to gain or lose electrons. Experiments with glass and silk rods illustrate the principles of electric charge attraction and repulsion.

Step-by-step explanation:

When you rub a balloon against a sweater, the balloon becomes negatively charged due to the transfer of electrons. This involves the interaction of static electricity, where certain materials can acquire a positive or negative charge through friction. In the classic experiment of mixing salt and pepper and using a charged balloon to separate them, the balloon attracts the pepper due to forces of static electricity. Notably, the pepper is not necessarily charged before the experiment. However, the pepper particles are more easily charged than the salt due to their smaller size and shape, and they can acquire an induced charge when subjected to an external electric field created by the charged balloon. This induced charge is opposite to that of the balloon, hence the attraction.

If you wish to predict how a charged balloon will interact with a given object, consider the material's propensity to gain or lose electrons and whether it currently has a net charge. The principle that like charges repel and unlike charges attract applies; therefore, if an object has a charge opposite to that of the balloon, it will be attracted, and if it has the same charge, it will be repelled. On the other hand, neutral items might experience polarization and could be attracted to the balloon due to induced charges.

Through various experiments, such as rubbing a glass rod with silk, we know there are two types of electric charge, termed 'positive' and 'negative'. These experiments show that materials with opposite charges attract each other, while those with like charges repel. This is demonstrated by the repulsion of two positively charged glass rods or two negatively charged pieces of silk. Similarly, a negatively charged balloon can attract neutral objects like the pepper particles through the process of polarization.