Electricity – electrons, insulators and conductors
The term ‘electricity’ comes from ‘elektron’, which is the Greek word for amber. The ancient Greeks discovered that small threads and dust tended to stick to their amber jewellery and that rubbing the amber, instead of removing the particles, only made the amber collect more debris. The urge to understand what caused the amber to attract threads and dust eventually led to our knowledge of electricity.
Amber pendant
An amber pendant from 500–480 BC. The ancient Greeks discovered that rubbing their amber jewellery to clear dust and other the particles only made the amber collect more debris. The urge to understand this eventually led to our current knowledge of electricity.
Electrons
Understanding atoms is key to understanding how electricity works. Atoms are made of protons, neutrons and electrons. An atom consists of one or more positively charged protons bound to one or more neutral neutrons. These are found in the centre of an atom called the nucleus, with one or more negatively charged electrons moving around them.
Electrons are loosely connected to the nucleus of an atom. They can literally be rubbed off some substances and deposited on others. This is exactly what was happening with the amber – by rubbing the amber with cloth, electrons are transferred from the amber and onto the cloth. Because the electrons are negatively charged, by removing electrons, the amber has fewer electrons than it had before and is said to be positively charged. Likewise, the cloth has collected the extra electrons and is said to be negatively charged.
Electricity is a difficult term to define. We think of electricity as the energy we use to power appliances in our homes and also as the bolt of lightning in a storm. In all cases, electricity involves electrons either moving from place to place in materials called conductors or building up on surfaces called insulators.
Insulators and conductors
In some materials such as glass, rubber, wood and most plastics, the electrons are held quite tightly and are not free to move easily from place to place. These materials are called insulators. In other materials such as copper, silver, gold and iron, electrons are free to move from place to place. These materials are called conductors.
Insulators and conductors – an analogy
An analogy is a comparison that helps to explain a complex idea by comparing it to something that is familiar. The following analogy uses ice cube trays, sultanas and water to explain how insulators and conductors work.
Electron movement in conductors and insulators
An analogy that can be used to explain the movement of electrons in conductors and insulators uses ice cube trays, sultanas and water.
Ice cube tray cut out by chatmali, licensed through 123RF Ltd.
Static electricity
Static electricity occurs when an object has electrons added to it or removed from it. Because electrons are negative, when an object has extra electrons, it is said to be negatively charged. When an object has had electrons removed, it is said to be positively charged. Static electricity causes many things we see every day. For example, a lightning bolt happens when the static charge on a storm clouds builds up and is then discharged to the Earth.
Electrons can be moved from one surface to another by rubbing. In this image, a child’s hair is standing on end after sliding down a plastic slide. Rubbing on the slide caused electrons to be moved from the child to the slide. This leaves the child positively charged. Because people can conduct electricity, the electrons came from all parts of his body, including his hair. We see the evidence of static electricity by observing his hair standing on end. Electrical charges behave much like magnets in that like charges repel each other. Because all of his hair is positively charged, it tries to get as far apart as possible by standing on end.
Hair-raising static electricity!
Rubbing on the plastic slide caused electrons to be moved from the child to the slide. This leaves the child positively charged. We see the evidence of static electricity by observing his hair standing on end.
Dynamic or current electricity
Dynamic or current electricity occurs when electrons are moving through an electrical conductor. The flow of electrons is known as an electrical current. An electrical current flows when you connect one end of a battery to the other with a conductor, with the electrons flowing from the negative side of the battery to the positive side much like water flows in a pipe.
Nature of science
Scientists over time have developed different models to explain atomic structure. The current thinking uses a model developed from quantum mechanics that uses a probability distribution for electrons around the atomic nucleus – electrons are moving around the atomic nucleus not in orbits but in areas of space. Of course, another way of representing an atom is by its relationship to the periodic table. As science evolves and technology discovers new ways to explore what we cannot see, our theories about atoms and their structure have changed. This is the nature of science in action.
Related content
Find out more about lightning.
This activity supports students to construct simple electrical circuits and test a variety of materials to identify those that are good conductors and those that do not conduct electricity.
This recorded professional learning session will build your confidence to teach aspects of the Physical World.
