18-1-electrical-charges-conservation-of-charge-and-transfer-of-charge_summary

The section Learning Objectives of this section are designed to help students understand and master the following standards: (5) The student knows the nature of forces in the physical world. The student is expected to: - Describe and calculate how the magnitude of the electrical force between two objects depends on their charges and the distance between them. - Characterize materials as conductors or insulators based on their electrical properties. This section focuses on the concept of electric charge, which is a property of matter that causes objects to attract or repel each other. Electric charge comes in two varieties, positive and negative. From the section, we learn that two positive charges repel each other, as do two negative charges. A positive charge and a negative charge attract each other. The scientific discovery of electric charge took several hundred years, with the fundamental particle that carries the negative unit of charge, the electron, being discovered in the late 19th century. The SI unit for electric charge is the coulomb, named after the French physicist Charles Augustin de Coulomb. The section also covers conservation of charge, the law that states that electrical charge cannot be created or destroyed. The law of conservation of charge is useful in that it allows us to keep track of electric charge in a system. In an isolated system, the net charge before and after any interaction within the system must be the same, provided that no external charge enters the system during the interaction and that no internal charge leaves the system. The section teaches us how to characterize materials as conductors or insulators based on their electrical properties. Conductors allow charge to move easily, while insulators do not. Insulating materials include plastics, glass, ceramics, and wood. Metals are good conductors. The conductivity of semiconductors is intermediate between that of conductors and insulators. The section introduces the concept of polarization, where an electrically neutral object becomes polarized when an electric field is applied to it. This polarization causes a separation of charges within the object, creating an electric dipole moment. The object remains electrically neutral but has a net internal electric field. The section also covers the transfer and separation of charge. Charge can be transferred by contact or induction. In charging by contact, the surfaces of two objects made of different materials are placed in close contact. Rubbing two surfaces together increases the transfer of electrons, because it creates a closer contact between the materials. Charging by induction occurs when a charged object is brought near an uncharged object. The uncharged object becomes polarized and can gain a charge by separation of charges. The laws of physics provide us with a solid foundation for understanding the world around us. Among these laws, the law of conservation of charge plays a crucial role in explaining how electric charge behaves and interacts with other objects. Understanding the fundamental properties of electric charge, including its conservation, is essential for anyone interested in the study of electricity and electronics.