Where to begin to understand Electrical Engineering?

If you are looking to understand Electricity, the first question that comes to anyone mind is where, to begin with. The first step shall be to learn and understand the initial discoveries which laid the foundation of electricity.

Historical facts of the origin of Electrical Engineering

In the year 1881, four units of measurements of Electricity namely ‘Columb’ ‘Volt’, ‘Ampere’ and ‘Ohm’ were announced to measure Voltage (or Electromotive force or potential difference), Current, Resistance and Charge to recognize the work of  Charles-Augustin de Coulomb 1736-1806,  Alessandro Volta  1745-1827, George Simon Ohm (1789-1854). These were the four discoveries and units of measurement from where begins the future of electrical engineering and which made our life comfortable today. Today, it may look to be a simple discovery, but it is difficult to believe how much intelligent and painstaking work has gone at the back for discovering such simple rules. It is also to understand the interdependence of the work of each of them. Columb discovered the behaviour of charge whereas Ampere discovered the behaviour of electric current and its magnetic effect. With the discovery of battery by Volt, it became possible for Ohm to conduct an experiment with ease about the amount of current flow and its dependence on resistance. It is undoubtedly the work of these great scientists who laid the foundation of all the future fields of electrical engineering.

Basics for Electrical Engineering

A subject of electrical engineering becomes very simple if basic fundamentals are understood. ‘Electron’ is the building block for all facets of Electricity. When it is static it results in the field of ‘Electro-Static’ and when moving it results in ‘Electro-dynamic’.

Does electricity originate from the work of Columb?

The static charge was studied in the 17th century by many scientists. Later on, Franklin with its popular kite experiment during the stormy and lightening time proved that charge flows. It was the work of Columb to understand the behaviour of static charges and the formulation of Coulomb’s law, which states that the force between two electrical charges is proportional to the product of the charges and inversely proportional to the square of the distance between them. Coulombic force is one of the principal forces involved in microscopic atomic structure and reactions. The unit coulomb was named after him and is defined as the quantity of electricity transported in one second by a current of one ampere. He also estimated that it is approximately equivalent to 6.24 × 10¹⁸ electrons. 

The study of Electro-static, as well as Electrodynamic, is part of Electrical Engineering having applications all around. Since the flow of electron is not visible and what and how it is doing its function, fundamental engineering is a must to master the understanding of its behaviour under the influence of various factors to visualize the effect and right interpretation using measuring instruments. In one-word, Electrical Engineering is a flow of electron and controlled in the manner to derive the advantage the engineer/scientist/innovator wants. It is the various controlling techniques that give birth to electrical, electronics, instrumentation, etc. Now, look at the basic fundamentals of the behaviour of electron flow and controlling techniques undergoing development every day.

What is the flow of the electron?

There are electrons in the outermost orbit of the nucleus of every material. These electrons are either bounded firmly or loosely with its nucleus. Where it is bonded loose, it produces a free electron which is always in random motion with high velocity and continuously colliding with each other resulting in zero average velocity. But when such free electrons are subjected to an electric field, it starts drifting; it attains an average velocity which is very small in the range of less than a centimetre per minute (much smaller than the slowest creature on earth “Banana Slug”).

What is the drift velocity of electron/charge?

This average velocity attained by an electron under the influence of the electric field is called drift velocity. Every electron possesses a charge equal to e=1.6×10^-19 coulombs and the number of a free electron in Copper is n=10²⁹ per m³. Therefore, the total charge in Copper shall be Q=1.6×10¹⁰ coulombs/m³. The rate of flow of charge is called current. Now under the application of an external electric field (also called Voltage), the electric charge starts drifting at drift velocity, which is in direct relation to the applied electric field.

Drift Velocity versus velocity of propagation of the electric field

The immediate question that will jump in anyone’s mind is ‘when the flow of electron is at such a very low average velocity, then how the lamp glows immediately when the switch is made ON“. If it is calculated based on the drift velocity, it will take a few hours. The reason is that the speed of propagation of the electric field from one end to another is at the velocity of light i.e. 3×108 m/sec and it is the electric field that drifts the charge at each location of the copper conductor. The charge close to the lamp filament starts doing its job immediately.

Relation between drift velocity, current and mobility of electron

 The flow of electron (charge) is also called current (on the analogy of flow water is also called water current). This current is determined by a simple formula (where n=10²⁹ per m³, e=1.6×10^-19 coulombs which are constant).

Hence the current depends on the area of cross-section and drift velocity. The drift velocity depends on the mobility of electron and applied electric field. Mobility depends on the property of a material and in turn, defines the ‘conductivity’ or ‘inverse of resistance’.

And therefore, the flow of electron depends on the property of the material and the applied electric field (Voltage). The International System of Units (SI) of current is Ampere (symbol A) and named after the André-Marie Ampère(1775–1836), a French mathematician and physicist, considered the father of electrodynamics and in recognition of his work to derive ‘Ampere’s Law’. He studied the behaviour of the flow of charge through a conductor and its magnetic property.  

Analogy

The flow of water is the best analogy to understand the flow of electron. The water flows under the water head (gravitation head or produced by a water pump). Similarly, the electron flows under the influence of Electric Field or Voltage or Electro-motive Force and equivalent to water head.

What is Voltage or Electro-motive Force?

When an external source is used for the electron (charge) to accumulate at one end of the conductor, the charge difference is called potential difference (and also called Voltage or Electro-motive force). A source of energy such as hydro, coal(steam), heat, solar radiation, wind, geothermal etc. is used for this.

Why Electricity is the most important source of Energy?

The most important feature of Electricity is its ability to produce using the available sources of energy and then transmit and utilize it at the consumer end. With alternating current, the transmission of electricity to vast distances became feasible. Thus, electrical energy has taken a dominant role as compared to any other form of energy in our daily life.

What is voltage?

The unit of Voltage or Emf or potential difference is volt (symbol: V) and is named after the Italian physicist Alessandro Volta (1745–1827). The work of Volta was developing an electric battery and initially termed the accumulation of charge as electromotive force (later called volt in the honour of Alessandro Volta). The invention of the electric battery simplified the laboratory set up for further work in the field of electric current.

It is defined as the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it. Following Ohm’s law, the volt is also defined as current flowing multiplied by the resistance.

What are the properties of the material that influences the flow of the electron?

As stated above, the mobility of an electron depends on the material and how the electrons are held with the nucleus of the element i.e. loose or strong bonding. In metals, electrons are held loose, and such material is called conductors, and when held firmly, such material is called insulators.

What is Ohm?

This property of material has led to defining the term ‘Resistance’ with the unit as Ohm (symbol Ω) named after the German Scientist George Simon Ohm. George Ohm did his work and measuring the flow of current with varying voltage and derived the relation between voltage, current and resistance and the influence of temperature. He also studied the influence of the cross-sectional area and the length of wire in the flow of charge. Resistance is the property of a substance due to which it opposes (or restricts) the flow of electrons (or current) through it.

Which are good conductors of electricity?

Those substances which have loosely held electrons and also offer the least difficulty in the mobility of electrons are good conductors of electricity ( and even heat). Metals (as a class), acids and salts solutions are good conductors of electricity. Amongst pure metals, silver, copper, and aluminium are very good conductors. These electrons while flowing pass through the molecules or the atoms of the conductor collide with other atoms and electrons, thereby loses energy and appear as heat.

Which are the bad conductors of electricity?

Those substances which have strongly held electrons and also offer relatively greater difficulty or hindrance to the passage of these electrons are said to be relatively poor conductors of electricity like Bakelite, mica, glass, rubber PVC (polyvinyl chloride) and dry wood, etc.

A good and bad conductor, both had an application in electrical engineering since it will require free as well as restricted movement depending on the requirement. The research work of Ohm was associated with a direct current of the battery, but today, it fits equally for an alternating current circuit (sufficiently complicated as compared to direct current) and magnetic circuit with ‘mmf’ equivalent of ’emf’ and ‘magnetic flux’ equivalent to ‘current’.

How the Electrical Engineering took shape in subsequent years?

The scientist, engineers, innovators found the electricity most useful in the service of humanity and worked upon continuously in all areas of making the electron flow as a carrier of energy and utilizing it wherever or whenever required. It is possible to control, restrict, stop and reverse the flow of charge and results in the development of various areas of Electrical Technologies. Some of the areas are as under:

1. Sources of energy and converting into electric energy: DC/AC/Battery/Solar/Wind/Hydropower/Coal base Generator/nuclear energy base generator/geothermal energy etc.;
2. The flow of current (or charge or electron) controlled with the help of material such as insulator, conductor, semi-conductor etc. Using gates either to pass or stop the flow of electron with the help of semi-conductors devices;
3. Transmission of electricity to far off distances at higher voltages;
4. The utilisation of electric energy in industry, house, commercial activity;
5. Electrical Safety;
6. Transportation- electric traction;
7. Electrical devices – motor, heating, illumination; and
8. Electrical Measurements and Instrumentation.

Conclusion

One can understand any complicated function of electricity by studying the behaviour of electron or charge. We should pay our tribute to the painstaking, methodical and intelligent work of all those great scientists, innovators and mathematicians whose work helped in developing of this great subject. The four great scientists who were honoured for their contribution were mathematics and Instrumentation are two important aspects that are the essential tools to distinguish each aspect with clarity and taking it forward in the right direction.

The Electrical Engineers salute you for your contribution towards the betterment of mankind.