Electricity is an important part of our everyday lives and is transmitted into our cities by huge transmission lines.
Figure 1. Electricity pylons.
What is electricity?
Electricity is defined as the collection of physical phenomena connected with the presence and motion of matter with an electric charge.
Lightning, static electricity, our appliances, electric discharges, and many other phenomena are all connected to the flow of individual charges. Let’s have a look at some of the characteristics of a single charge:
- An electric field E is created by the existence of an individual electric charge, which can be positive or negative. The field is also generated by a body with an electric charge or a group of charged particles.
- A magnetic field H is created by the movement of electric charges.
- A force F acts on a charge when it is put in an area where an electric field is present. Coulomb’s law determines the amount of this force.
- The electric field impacts the electric charge if it moves inside it.
Electric current
The flow of an electric charge is known as electric current I. This is widely used in the technology that powers circuits and mechanical devices. The electric charge Q divided by time gives us the value of the current, which is measured using the SI (Standard International) unit ampere (A).
\[I = \frac{Q}{t}\]
Electric potential
Electric potential, also known as voltage (V), is the work done by an external force in transporting a unit of electric charge from point A to point B. This is done against an electric field without acceleration, and it is generally measured in volts (V).
Electric power is the rate at which electrical energy is transferred by an electric circuit. It is, therefore, work W divided by time t. The SI unit of electric power is the watt (W), which is equal to joules (the unit of work) per second. Electric power is generated by electric generators and transferred using the power grid.
\[P = \frac{W}{t}\]
Resistance
Resistance is the opposition presented to the flow of current, which varies depending on each material. The SI unit of resistance is the ohm (Ω).
An important relationship between the electric potential, the current, and resistance is defined as follows: for fixed electric potential, current and resistance are inversely proportional to each other.
Their relation is expressed as follows:
\[R = \frac{V}{I}\]
Resistivity
The resistivity (ρ) of a material is the resistance presented by a conductor when the charge flow depends on the conductor’s area A and length l. In this case, as the material conducting electricity has a larger area or length, its resistivity will vary. The SI unit of resistivity is ohm per metre (Ω / m).
\[\rho = R \cdot \frac{A}{l}\]
The inverse of resistivity is known as conductivity σ, which is defined as the property that determines how easily a conductor allows charge flow.
\[\sigma = \frac{1}{\rho}\]
Circuit components
A circuit component is a device or object that is used in circuits to store energy, limit current flow, or perform other useful functions. Some examples of circuit components include:
Superconductivity
Superconductivity is the property of a conductor to offer zero resistance to the flow of current. Superconductors, therefore, are materials that offer near-zero resistance at a temperature known as the critical temperature. For the critical temperatures of some materials, see the table below.
Material | Critical temperature in Kelvin |
Gallium | 1.1 |
Lead | 7.2 |
Mercury | 4.2 |
Tungsten | 0.01 |
The critical temperatures found so far for any conductor material are very low, usually far below zero Celsius and very close to zero Kelvin (-273.16 Celsius).
What is the history of electricity?
There is no single defining moment in the history of electricity. Nearly 300 years of study and development have gone into the way we generate, distribute, install, and use electricity, as well as the devices it powers.
Electricity was first studied, captured, and tamed in the 18th century. Hundreds of ‘natural scientists’ in England, Europe, and northern America studied electricity in nature over the next 150 years, but generating it outside of nature was a different challenge.
This did not happen on a wide basis until the late 1800s. International scholars engaged in pure scientific study, as well as enterprising business people, who made their own important discoveries or created, promoted, and sold goods based on other people’s ideas, helped pave the way for the broad commercial usage of electricity.
Here is a timeline of the evolution of electricity:
- 1752: Benjamin Franklin shows that lightning and electricity are the same phenomena.
- 1800: First Battery invented by Alessandro Volta.
- 1821: Michael Faraday creates the first electric motor.
- 1826: Georg Ohm discovers the relationship between resistance, current, and voltage, also known as Ohm’s law.
- 1831: Induction ring invented by Michael Faraday.
- 1832: First dynamo invented in France by Hippolyte Pixii.
- 1834: First American DC motor constructed by Thomas Davenport.
- 1835: Electrical relay invented by Joseph Henry.
- 1839: William Robert Grove invents the first fuel cell.
- 1860s: Theory of electromagnetic fields developed by James Clerk Maxwell.
- 1876: Open coil dynamo invented by Charles F. Brush.
- 1878: First incandescent light bulb invented by Joseph Swan is shown to the Newcastle Chemical Society.
- 1879: Incandescent light bulb working 40 hours invented by Thomas Edison.
- 1879: Brush arc lamp invented.
- 1881: Electric streetcar invented by Gustave Trouvé.
- 1882: First electric power station opened.
- 1883: Tesla coil invented.
- 1884: Electric alternator invented.
- 1886: Induction coil transformer and alternating current electric system developed.
- 1888: Nikola Tesla invents the first modern alternating current system.
- 1893: AC used for the first time to light street lamps.
- 1897: Electron discovered by J. J. Thomson.
Electricity - key takeaways
- An electric field is created by the existence of an electric charge.
- The electric field impacts the electric charge if it moves inside it.
- The SI unit of electric power is the watt, which is equal to joules per second.
- Electrical energy is the energy harnessed by the movement of electrons.
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