From the static cling in clothes fresh out of the dryer to the dazzling displays of lightning during thunderstorms, humans have been fascinated by electric charge for millennia.
The ancient Greeks were among the first to observe static electricity when they rubbed amber with cloth, producing forces of attraction and repulsion. In fact, our word "electron" comes from the Greek word for amber, ἤλεκτρον (elektron).
ut what actually is charge? While our understanding has advanced significantly over the last 300 years, physics primarily describes how charge behaves rather than what fundamentally creates it.
In this introductory series, we will explore what electric charge is, how it is quantified, and how charged objects behave. Later lessons will cover charges in motion—such as electric current in circuits—as well as how charges interact within electric and magnetic fields
An introduction to Electric Charge
Here are two demonstrations that are done in the classroom. They demonstrate the conservation of charge.
Starting with a historical overview of our understanding of electrical charge. this video examines the basis of electrical charge, namely the electron and the proton. It's only also examines one of the conservation laws, concept of conservation of charge.
This simple simulation from pHET shows how you can 'stick' a balloon to a wall, using the concept of conservation of charge.
Going Deeper
In the video I discussed how ultimately a charge is determined by the number of electrons and protons present in the material. The presumption is that electrical charge at a fundamental level is discrete, based on the number of protons and electrons.
However this is problematic.
Electrons, based on the standard model are a fundamental particle. That is, they are indivisible and so if we assign a discrete value to charge we often assign it with a -1. Consequently, we assign a +1 charge to the proton. Therefore in a neutral atom, we have the same number of protons and electrons.
But protons are not fundamental particles. According to the Standard Model, protons are particle groups, made up of quarks, two up quarks and one down quark. As a result the up quark has a charge of +2/3, and the down quark has a charge of a -1/3.
So although charge is a discrete value, the values of +1 and -1 arbitrary.
You can see more on the standard model here