Question

A student in your class is confused about the balloon sticking to the wall. She makes the following statement:

We studied Coulomb’s Law in class. Coulomb’s Law states that the electric force between two charged objects is proportional to the product of their charges (F ~ q₁q₂). I know the balloon is charged, it’s clear that there is a net charge if I toggle “show charge differences” in the simulation. However, the wall shows no charge difference, it’s still neutral, which means its charge is zero. Anything times zero is zero, so how can there be a force between the wall and the balloon?

Can you help your classmate explain this challenging problem?

Answer 1

Theory : Dipole moment : On presence of external Field the neutral atoms of the wall get polarised with one type of charges facing ballon and the other type facing away  

Solution:

The approach to solve such questions is to go step by step

The ballon is charged baloon as stated,.

The charged ballon definitely has some electric field

The ballon when goes near the wall , induces dipoles in the wall.

I.e let's say the ballon is positively charged , this charged tries to exert force on neutral atoms on the wall,

The neutral atoms of wall form dipoles and negative part of atom faces the ballon and positive part faces away from ballon ,  

The neraby positive and negative parts of atoms in the wall sum to zero, but the egdes have induced charges because of charge of ballon , and hence have net electric field and attract the ballon to it.

The best life example is from chapter Magnetism:

Normally Iron doesn't attract anything towards it , but why does it attract a magnet, beacuse on bringing magnet towards it , magnetic dipole field induces in the iron