1.1 THE BASICS OF ELECTRICITY 1 Other even smaller particles called quarks have been discovered inside the nucleus of atoms. It is a property of materials to have electrons that can move more or less freely among atoms; according to this property, materials are divided into conductors and insulators (see page 16). Have you experienced static in other ways? Find out something more about Coulomb on the Internet. ONLINE RESOURCES Static electricity appliance: apparecchiatura to bind: legare device: dispositivo fur: pelliccia matter: materia to orbit: orbitare to repel: respingere to rub: strofinare several: molti strength: forza ELECTRICITY AND ELECTRIC CHARGE Electricity is a phenomenon that we all know very well. Most of the appliances or devices that we use every day work thanks to it. The discovery of electricity The word electricity comes from the ancient Greek word ele ktro n, which means amber; at that time, people had discovered that a piece of amber rubbed with animal fur could attract small leaves of dried grass. This phenomenon would be understood many centuries later, when technology made it possible to look deeper inside matter and its structure. The structure of matter: atoms Matter is composed by atoms which, for several centuries, were considered its smallest parts. Since the end of the 19th century, however, we have known that atoms consist of smaller particles called protons and neutrons, strongly bound together to form the nucleus, while other particles, called electrons , orbit around the nucleus and are able to move from one atom to another . Protons carry a positive electric charge, neutrons are neutral, and electrons carry a negative electric charge. Electric fields The number of protons and electrons in an atom is the same, so atoms are normally neutral. However, when an atom loses or gains electrons, it becomes either a positive or a negative ion respectively. In this situation, objects get an electric charge, the strength of which is proportional to the quantity of electrons moving from atom to atom. For example, when a balloon is rubbed against someone s hair, the balloon and the hair become attracted to each other and the hair sticks up. This happens because the rubbing action makes electrons move from the hair, which becomes positively charged, to the balloon, which gains a negative charge and attracts it. The two charged bodies create an electric field, that works to attract them. This attractive force is called static or electrostatic and was observed and studied by Coulomb in the late 18th century. Two bodies with opposite charges attract each other; when two bodies have like charges, on the contrary, their electric fields repel each other. 12 Elettronica-Informatica.indb 12 25/01/24 16:07