2.1 THE BASICS OF ELECTRICITY 13 The word atom derives from the Greek word for indivisible. Other even smaller particles called quarks have been discovered inside the nucleus of atoms. Have you ever experienced static in other ways? ONLINE RESOURCES The war of the currents appliance: apparecchiatura to bind: legare fur: pelliccia matter: materia to repel: respingere to rub: strofinare soldering iron: saldatore vacuum cleaner: aspirapolvere ELECTRICITY Electricity is so important in our lives that we cannot do without it. Electricity operates devices, such as smartphones, tablets or computers, and appliances, such as vacuum cleaners, microwave ovens, soldering irons and drills commonly used at home, at school or in workplaces. The discovery of electricity The word electricity comes from the ancient Greek word elektron, which means amber; as at that time, people had discovered that a piece of amber rubbed with animal fur could attract small leaves of dried grass. However, this phenomenon was only understood many centuries later, when technology made it possible to look deeper inside 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. Ions 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, whose strength is proportional to the quantity of electrons moving from atom to atom. atom structure Proton Neutron Electron Electrostatic force When a plastic pen is rubbed against a piece of cloth, it attracts small pieces of paper. This happens because the rubbing action makes electrons move from the cloth, which becomes positively charged, to the pen, which gains a negative charge and attracts paper. This attractive force is called static or electrostatic : two bodies with opposite charges attract each other; while two bodies having the same charge repel each other. electrical force Attract Repel Atoms which gain an electron form a negative ion 46 elecTriciTy Atoms which lose an electron form a positive ion