Electricity

The flow of electric charge

What is electricity?

Electricity is the flow of electric charge. Charge is a property of matter that can be measured (just like mass, volume or density).

Electric charge can be positive or negative. To move charge we need something to carry this charge. These charge carriers are typically electrons, which are found in atoms.

A force exists between two charges. If the charges are the same, they repel (push away) one another. If the charges are different, they attract (pull closer) one another. Opposites attract, and likes repel.

The closer two charges get, the greater the force of attraction or repulsion between them. This force is called the electrostatic force.

Consider a copper atom, which has 29 electrons orbiting around its nucleus. These electrons orbit the nucleus in layers and on the outer most layer there is one electron.

This is called the valance electron. It’s the furthest away from the positively charged nucleus. So, this electron requires the least amount of electrostatic force to free it from the atom.

If we have a copper wire, we can push valences electrons from one copper atom to another to create a flow of electrons, which is called an electric current.

Some materials are better at releasing their electrons than others. A material’s conductivity measures how tightly bound an electron is to an atom.

Some materials (like copper) have very mobile electrons. They have a high conductivity and are called conductors.

Materials with low conductivity (like glass or rubber) are called insulators.

Types of electricity

There are two types of electricity: static and current electricity.

Static electricity occurs when two opposite charges build up but are separated by an insulator. Eventually, the attraction between the two charges becomes so great that they can flow through the insulator to equalise the charges. This is called a static discharge. Lightning is an example of a static discharge.

Current electricity exists when charges can constantly flow. It’s current electricity that makes all of our electronic devices work.

Current in metal wires is pushed along by a voltage. If the voltage comes from a battery, the electrons flow in one direction. This is called direct current (DC).

If the electrons constantly switch direction (alternate) then we call this alternating current (AC). With AC, the power distribution is more efficient than DC. So, AC is predominantly used for high power applications.

So what?

Electricity is a weightless, versatile and easy-to-control form of energy. It’s a vital part of our day-to-day lives.

At the point of use, it’s practically loss-free and non-polluting. Electricity can be created from a variety of methods, including solar power, hydropower, wind power, natural gas and nuclear power. It can also be converted into other types of energy.

What else?

Electricity has had a turbulent past. In the late 19th century, two scientific powerhouses (Nikola Tesla and Thomas Edison) fought over whether alternating current (AC) or direct current (DC) would power the modern world. Edison was in favour of DC and used scare tactics (including electrocuting animals) to demonstrate the danger of AC. Tesla and his AC system ultimately won.

Want more?

Here’s a wonderful Royal Institution talk from Dr Marty Jopson who leads us through the story of electricity in a show filled with demonstrations.

Electrickery

Melvyn Bragg and guests discuss the dawn of the age of electricity.

Nikola Tesla

A (slightly sweary) biography of Tesla from The Oatmeal online comic.

Ohmify

A friendly community with lots of electronics projects to get started on.

Special relativity

Quantum Mechanics
November 8, 2019

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