In this tutorial, we shall discuss the concept of electricity and electric charges. Before we delve into details, it would be better to emphasis what we already know.
What is Electricity?
In a brief and easy to understand definition, we can refer to electricity as “electric charge in motion“. I.e. electricity is produced when charges move. In other words, if charges are not in motion, we do not have electricity. Hmm, that’s a simple definition. Then, what is electric charge?
What is Electric Charge?
Well, I’m afraid there is no simple definition for that. For one to understand what electric charge is, a deeper and intuitive explanation is needed. Hence let’s delve into the mystery and get it demystified.
The Physics of Electric Charges
It all started with an atom. Basically, we know that atoms are made up of three fundamental particles, neutron, proton and electron. But that is not all there is, as a matter of fact we have many subatomic particles, e.g. “quarks” with complex classifications, but that is too much of physics, let’s not go there. A better understanding of the three basic subatomic particles will give us an intuitive knowledge of what an electric charge is, especially the electron and proton.
An atom has the following particles
- a proton (which carries a positive charge)
- an electron (which carries a negative charge)
- a neutron (which carries no charge)
The proton and neutron are located at the center of an atom, while the electron maybe found somewhere around the atom in regions called orbitals.
Orbitals are regions around an atom where an electron is likely to be found. We traditionally assume that electrons move round an atom, well, that could be true but not necessarily true, suffice it to say that electrons exercise jumps round an atom with respect to the energy they have. What am I saying? What I’m saying is that if an electron moves round an atom as we conceive it to, it will keep moving until it loses all its energy and collapse to the nucleus (center of the atom) of the atom, but we know that doesn’t happen. What happens is that, electrons in an atom have energies; the energy of an electron determines its location in an atom. An electron with small energy will reside close to the nucleus, while electron with higher energy will jump to a higher position in the nucleus.
The image below gives a better intuition into the understanding of the atom.
Let the green balls be the protons and the orange balls are the neutrons. The yellow circles are the orbits within the orbitals, while the yellow balls orbiting the nucleus are the electrons. The circular paths the electrons create are determined by the angular momentum of the electron. Though the image depicts the electrons constantly moving round the nucleus that is not what continuously happens, the orbit shown gives the path an electron can take when it is excited to move from a lower energy state to a higher energy state. On the other hand, since an electron can behave like a wave too, you can see the cyclic paths as a standing wave created from the energy states of the electrons.
Having discussed a brief physics of atoms, let’s move forward to answer the pressing question what is an electric charge.
Categorically, an electron carries a negative charge, while a proton carries a positive charge and a neutron has no charge. Charges are inherent properties of an electron and a proton which can be clearly observed when they are distanced from each other. Sometimes we refer to charges as “electric charges” this is because these charges have the tendency to move, and when charges move they are called electricity. Remember the definition we gave at the beginning.
From this definition, we can see that a charge exists only when there is excess of electron or excess of proton, because this will mean that for one negative charge to exist, it means that one positive charge has been distanced from that negative charge within the system under consideration.
See image below:
The image above shows an atom with 3 electrons and 3 protons. Since the positive and negative charges balance, i.e. -3+3 = 0, the atom does not have a net charge; hence the atom is electrically neutral.
However, if for any reason, there is loss of a proton from the atom as depicted in figure 2 below
Then we would have a net negative charge in the atomic system, i.e. -3+2 = -1. These -1 shows we have a net negative charge which carries a charge value of -1.6 x10-19, so if we have excess of 2 electrons instead of 1, we would have 2*-1.6×10-19 = -3.2×10-19. This simply means that electric “charges are quantized” a concept called Quantization of electric charge. We cannot have an electric charge having a fraction of the value ±1.6×10-19, it will either be ±1.6×10-19 or integer multiple of ±1.6×10-19.Electric charge value = nq, where n= integer and q =1.6×10-19.
For the atom above having 2 electrons and 3 protons, the excess proton gives the atom a net positive charge with same charge magnitude of 1.6×10-19, but positively charged.
Static as the name implies mean that the charge is non-dynamic. The charge is stable. These charges that are generated when for any reason an electron is either removed or added to a body, and remain where they are generated is called static charges. However, when for any reason these charges tend to move, maybe when they are attracted by another oppositely charged body, they become “static electricity”
How to generate static charge and static electricity
Fundamentally, static electric charges are friction induced charges; we mostly obtain them when two bodies are in repeated contact. The effect of producing electric charges when two bodies are rubbed is called “Triboelectric Effect or Triboelectricity”. Some bodies gain charges when rubbed with another, while some don’t. Those that do gain charges when rubbed will gain either positive or negative charges. There is a series that shows the list of triboelectric materials (Conductors or insulators)
Conductors and Insulators
Conductors are materials that allow electric current to easily pass through them, while insulators or non-conductors are those materials that do not allow electric current to easily pass through them and their respective inducible charges. This series is called “Triboelectric series”
When you rub materials that are very near in the series, you may find it difficult to generate static charges, but when you rub two materials far separated in the series, you will get a very strong static charge. Static charges have both advantages and disadvantages. One of the advantages is its use in the design of laser jet printers. However, a very big disadvantage is the stray static charges that can damage sensitive electronic components. Hence, as an electronic circuit designer, you do not wear cloths made of wool while working with electronic components, because when wool rubs with another material, it can easily generate static charges which can damage sensitive electronic parts. Wearing cloths made of cotton will be a recommendation.
Unit of electric charge
Electric charges can be quantified. The unit of electric charge is coulomb abbreviated as C. so; one electron has a charge of -1.6×10-19 C
Electric current and charge is related by the formula
Electric Current = Charge / Time
I have written a tutorial titled “difference between Current and Voltage“. There we discuss current, voltage and charges with easy to understand images.
Properties of Electric Charge
From the ideas we’ve hinted so far, we can derive three basic properties of electric charges.
- Charges add up
- Charges are conserved
- Charges are quantized
So far, we have been able to establish facts about static charges and static electricity, it should be noted that a good understanding of these concepts will help one to have a better understanding and appreciation of electronics.