1.1 THE BASICS OF ELECTRICITY ELECTRICITY AND ELECTRIC CHARGE Electricity is a phenomenon that we all know very well. Most of the or that we use every day work thanks to it. appliances devices The discovery of electricity The word comes from the ancient Greek word , which means ; at that time, people had discovered that a piece of amber with animal could attract small leaves of dried grass. This phenomenon would be understood many centuries later, when technology made it possible to look deeper inside and its structure. electricity ēlektron amber rubbed fur matter The structure of matter: atoms Matter is composed by which, for centuries, were considered its smallest parts. Since the end of the 19 century, however, we have known that atoms consist of smaller particles called and , strongly together to form the , while other particles, called , 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. atoms several th protons neutrons bound nucleus electrons 1 orbit 2 MORE Other even smaller particles called have been discovered inside the nucleus of atoms. 1 quarks MORE 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 and (see page 16). 2 conductors insulators 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 or a ion respectively. In this situation, objects get an electric charge, the 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 , that works to attract them. This attractive force is called or and was observed and studied by Coulomb in the late 18 century. Two bodies with opposite charges attract each other; when two bodies have like charges, on the contrary, their electric fields each other. positive negative strength electric field static electrostatic 1 2 th repel DO Have you experienced static in other ways? 1 DO Find out something more about Coulomb on the Internet. 2 ONLINE RESOURCES Static electricity