Electricity - History and Basic Theory
This article presents in simple terms the history and basic theory of electricity with the aim to bring the science and technology to the understanding of ordinary people.
Electricity has driven the Second Industrial Revolution and continues to shape our culture and yet basic understanding of this phenomenon lacks to most people except those trained in the industry.
Modern science of electricity had been evolving in the past 300 - 500 years. Today electricity is part of our culture. We all need to have the basic understanding of where we came from regarding electricity and where we are now.
Electricity is a natural effect that had been experienced by human beings since antiquity, most likely through lightning, statics and in our biological make-up, fish exhibit electricity effects more than any other animal.
Histroy Of Electricity Through The Ages
- Ancient Times: Electricity as a natural phenomenon had been observed in fish - Ancient Egyptian texts refer to certain fish as "Thunderer of the Nile" due to their electric effects.
- 1500: The Arabs use the term raad a term for lightning to refer to the electric ray (a type of fish that produces an electric discharge) thereby providing the earliest link between lightning and electricity
- 1600: William Gilbert coined the Latin term electricus to refer to electricity.
- Further work by Otto von Guericke, Robert Boyle, Stephen Gray, C.F. du Fay followed.
- 1752: Benjamin Franklin, an American statesman, carried out extensive experiments on electricity which he sponsored using his personal fortune. He carried out one very dangerous experiment which proved that lightning was indeed an electrical phenomena.
- 1791: Luigi Galvani demonstrated that electricity was the medium through which nerve cells transmitted messages to the muscles.
- 1800: Alessandro Volta created the voltaic pile, a stack of zinc plates alternating with copper plates to produce the first reliable source of electricity. The battery, before that electricity was produced by some static electricity generators.
- 1820-1821: Hans Christian Orsted and Andre-Marie Ampere: Orsted demonstrated that electrical current produced magnetism, Ampere developed and refined the mathematical structure: these two demonstrated the unity of magnetism and electricity.
- 1821: Michael Faraday invented the electric motor.
- 1827: Georg Ohm provided the first mathematical analysis of the electric circuit.
- 1861 and 1862: James Clerk Maxwell in his paper " On Physical Lines of Force" demonstrated that electricity, magnetism and light were one phenomenon in a set of equations, the famous Maxwell's Equations , which are considered as some of the most fundamental in the description of nature.
- Late 19th century was the beginning of electrical engineering as separate from the early scientific interest and the following scientists were the pioneers of practical application of electricity:
- Alexander Graham Bell
- Otto Blathy
- Galelio Ferraris
- Oliver Heaviside
- Anyos Jedlik
- Lord Kelvin
- Sir Charles Parsons
- Ernst Werner Siemens
- Joseph Swan
- Nikola Tesla
- George Westinghouse
As said above, the late 19th century scientists were engineers who transitioned the study from a mere curiosity to a commercial and cultural concern necessary for ordinary day life. The Second Industrial Revolution was driven by electricity.
In 1887 Heinrich Hertz discovered the photoelectric phenomenon and it was left for Albert Einstein to explain in 1905 it as a quantum process, earning himself a Nobel Prize.
Progress continues up today.
Nature of Electricity
Electricity occurs naturally in two forms, as static electricity or as electrical current. Electrostatics is the study of charged bodies where there is isolation of charge or a body where charge is stored.
When there is a discharge, then an electrical current flows. Therefore electricity can be said as flow of electric charge.
The basic theory necessary for our discussion in this article is that discovered by Orsted and mathematically refined by Ampere. This can be stated as follows:
- An electrical current produces a magentic field and
- A changing magnetic field produces an electrical current
- Interacting current carrying conductors produce mechanical force (of attraction or repelling)
Understanding these three principles will be useful throughout this article to show how things work. Theory will be kept to the minimum , only that required to understand how electricity works .
Generating Electricity From A Changing Magnetic Field
A basic high school science experiment involves
- two magnets placed facing each other
- a copper wire placed between the two magnet ends and connected to a current measuring equipment or to a light bulb and the students to conduct and observe the experiment
- at least one of the students must move (i) either the set of magnets up and down or (ii) the wire
- It will be observed that when the wire is moved up and down between the magnet poles, the light bulb will light up. The same observation is made if the the conductor was moved instead of the magnet
The experiment demonstrates that : moving a conducting wire across a magnetic field produces electricity.
Or: a changing magnetic field produces electricity.
Also to be observed is that kinetic energy can be converted to electrical energy.
Wind Power - Example of Mechanical Energy Convertion to Electrical Energy
Definitions & Formulae
Basic Unit of Electricity, either positive or negative
Rate of flow of charge per unit time, I = q/t
Voltage , Potential Difference, V
The energy required to move a unit charge from one point in a circuit to another, E = q x V
Power , P
Rate of conversion of energy from one form to another, P = E/t = (q x V)/t = IV = IxIxR (I squared R)
Relationship between the Voltage across a passive component and Current flowing through it R = V/I
Producing Magnetism From Electric Current
Another high school experiement involves the following:
- Iron filings
- A copper conductor connetected to a source of electricity
- Students to monitor and record
It will be observed that when the switch is closed and current is flowing, if the iron filings are placed near the conductor, they will align as if a magnet was near them.
The experiement proves that an electrical current produces magnetism.
Interacting Current Carrying Conductors Produces Mechanical Force
Two current carrying conductors placed side by side will either pull or repel each other depending on the direction of currents.
This effect is a direct consequence of the fact that a current carrying conductor will will produce magnetic effect. Therefore two current carrying conductors will have interacting magnetic fields.
The practical implication is that electrical energy can be converted to kinetic (mechanical ) energy.
Production of electrical energy from mechanical energy
In a generator, three things happen, an electrical current produces a magnetic field. A mechanical power system drives rotor to create a changing magnetic field and thus the varying magnetic field produces electricity
Stepping up or stepping down voltage from one voltage level to another
A transformer is an example of an electromagnetic equipment where a varying electrical current produces a varying magnetic field which in turn produces a varying electrical current!
Bulk transfer of electrical energy
A typical electromagnetic wave
Production of mechanical energy from electrical energy
Typical case of two current carrying conductors