Electricity is a phenomenon that occurs throughout nature and takes many different forms. It is briefly defined as the flow of electric charge. To understand the fundamentals of electricity, we need to begin with the construction of atoms, the basic building blocks of everything. Atoms exist in different forms as chemical elements like hydrogen, carbon, oxygen, copper in total 118. When atoms combine to form molecules, they get a new function and characteristic. They become part of the total.
An atom is built from three particles: electrons, protons, and neutrons. Each atom has a central nucleus, where the protons and neutrons are packed together. Surrounding a nucleus is a group of orbiting electrons.
A model atom. The nucleus is made of protons and neutrons and surrounded by orbiting electrons.
Every atom has at least one proton in it. The number of protons in an atom defines what chemical element the atom represents. For example, an atom with just one proton is hydrogen, an atom with 29 protons is copper, and an atom with 94 protons is plutonium. This count of protons is called the atom’s atomic number.
The protons are held at a place in the nucleus by neutrons which also determine the isotope of an atom.
Electrons are essential to the workings of electricity. In its most balanced state, an atom has the same number of electrons as protons. In the Bohr atom model below, a nucleus with 29 protons (a copper atom) is surrounded by an equal number of electrons.
The Bohr model is a very useful atom model as we explore electricity. The atom’s electrons aren’t all forever bound to the atom. The electrons on the outer orbit of the atom are called valence electrons. With enough outside force, a valence electron can escape the orbit of the atom and become free. Free electrons allow us to move charge, which is what electricity is.
The charge is measurable. The key concept with charge is that it can come in two types: positive (+) or negative (-). In order to move charge, we need charge carriers. Electrons always carry a negative charge, while protons are always positively charged. Neutrons are neutral, they have no charge. Both electrons and protons carry the same amount of charge, just the opposite type.
A lithium atom (3 protons) model with the charges labeled.
The charge of electrons and protons is important because it provides us the way to exert a force on them.
Electrostatic force (also called Coulomb’s law) is a force that operates between charges. It states that charges of the same type repel each other, while charges of opposite types are attracted together. Opposites attract, and likes repel.
The amount of force acting on two charges depends on how far they are from each other. The closer two charges get, the greater the force (either pushing together or pulling away) becomes.
With electrostatic force, electrons push away other electrons and are attracted to protons. This force is part of the “force” that holds atoms together, it’s the tool we need to make electrons (and charges) flow!
Making Charges Flow
Electrons in atoms can act as the charge carrier, every electron carries a negative charge. If we can free an electron from an atom and control it to move, we create electricity. Copper is known as a conductor. In its balanced state, copper has 29 protons and 35 neutrons in its nucleus and an equal number of 29 electrons orbiting around it. Electrons closer to the nucleus have a stronger attraction to the center than those in distant orbits. The outermost electrons of an atom are called the valence electrons, these require the least amount of force to be freed from an atom.
This is a copper atom diagram: 29 protons in the nucleus, surrounded by bands of circling electrons. Electrons closer to the nucleus are hard to remove while the valence (outer ring) electron requires relatively little energy to be ejected from the atom.
Using enough electrostatic force on the valence electron–either pushing it with another negative charge or attracting it with a positive charge–we free the electron from orbit around the atom creating a free electron.
A copper wire is full of these “free” electrons. As the free electron is floating in a space between atoms, it’s pulled and prodded by surrounding charges in that space. The free electron seeks a new atom to latch on to; in doing so, the negative charge of that electron ejects another valence electron from the atom. The “new” electron is drifting through free space looking to do the same. This chain effect can continue on and on to create a flow of electrons called an electric current.