1.2 THE PRODUCTION OF ELECTRICITY 9 The lead acid contained in car batteries is a corrosive liquid which is dangerous when it leaks. For this reason, some car manufacturing companies, mainly located in China, are working to produce batteries with a solid electrolyte, to be used along with the traditional liquid electrolyte ones. BATTERIES Batteries are devices that produce and store electrical energy obtained by a chemical reaction. Batteries make it possible to use portable appliances or devices everywhere, without the need of plugging them in or using wires and cables. The components of a battery All batteries consist of one or more cells. A cell is the basic unit of a battery, and is composed of three fundamental elements, enclosed in a plastic or metal case: a positive electrode, called cathode; a negative electrode, called anode; an electrolyte, which can be a liquid or a paste, in which the electrodes are partially immersed. How batteries work The electrolyte is a chemical with great conductivity which allows the flow of electrical charge between the cathode and the anode. The two electrodes are generally made of different materials, for example carbon and zinc, and have an end (or terminal) that extends out of the ONLINE RESOURCES Kinetic and potential energy Cathode (+) Separator Brass nail Electrolyte Anode ( ) case: contenitore chemical: sostanza chimica hearing aid: apparecchio acustico hydride: idruro lead: piombo to leak: fuoriuscire 28 case. The metal of the anode, reacting with the electrolyte, releases electrons which are caught by the cathode, itself reacting chemically to the electrolyte, too. When the two terminals are connected by a wire, a circuit is formed; the metal electrons will flow through the wire and the current can power any device that is connected to it. When this electrochemical process comes to an end, electrons cannot be produced anymore; as soon as this happens, the battery becomes exhausted and stops powering the devices connected to it. Different types of batteries Batteries can be divided into two big categories: Primary (non-rechargeable), such as: Zinc-carbon batteries, which are very cheap and employed, for example, in small toys; Alkaline batteries, which provide a good amount of energy, are relatively cheap and are used for motorised toys, shavers, or flashlights; Silver-oxide and zinc-air batteries, which have the shape of a small, flat button and are used for watches and hearing aids. Secondary (rechargeable), such as: Lithium-ion (li-ion) and lithiumpolymer (li-po) batteries, which are typically used in smartphones, tablets and laptops, are quick to recharge and discharge slowly; Nickel-metal hydride batteries (NiMH), which are used, for example, in digital cameras, power drills and in industry; Lead-acid batteries, which are mainly employed in motor vehicles and for emergency lighting. elecTriciTy aND iTs aPPlicaTioNs Elettronica-Informatica.indb 28 25/01/24 16:07