Basic Electrical Engineering Lecture NO. 1 The Nature of Electricity STRUCTURE OF THE ATOM Matter is anything that has mass and occupies space. Matter is composed of very small particles called atoms. All matter can be classified into either one of two groups: elements or compounds. In an element, all the atoms are the same. Examples of elements are aluminum, copper, carbon, germanium, and silicon. A compound is a combination of elements. Water,for example, is a compound consisting of the elements hydrogen and oxygen. The smallest particle of any compound that retains the original characteristics of that compound is called a molecule. Atoms are composed of subatomic particles of electrons, protons, and neutrons in various combinations. The electron is the fundamental negative charge (-) of electricity. Electrons revolve about the nucleus or center of the atom in paths of concentric “shells,” or orbits (Fig.1- 1). The proton is the fundamental positive (+) charge of electricity. Protons are found in the nucleus. The number of protons within the nucleus of any particular atom specifies the atomic number of that atom. For example, the silicon atom has 14 protons in its nucleus so the atomic number of silicon is 14. The neutron, which is the fundamental neutral charge of electricity, is also found in the nucleus. Atoms of different elements differ from one another in the number of electrons and protons they contain .In its natural state, an atom of any element contains an equal number of electrons and protons. Since the negative (-) charge of each electron is equal in magnitude to the positive (+) charge of each proton, the two opposite charges cancel. An atom in this condition is electrically neutral, or in balance . Example 1.1 Describe the two simplest atoms. Example 1.2 Describe what happens to the copper atom when it loses an electron from its outermost shell. THE ELECTRIC CHARGE Since some atoms can lose electrons and other atoms can gain electrons, it is possible to cause a transfer of electrons from one object to another. When this takes place, the equal distribution of the positive and negative charges in each object no longer exists. Therefore, one object will contain an excess number of electrons and its charge must have a negative, or minus (-), electric polarity. The other object will contain an excess number of protons and its charge must have a positive, or plus (+), polarity. When a pair of objects contains the same charge, that is, both positive (+) or both negative(-), the objects are said to have like charges. When a pair of bodies contains different charges, that is, one body is positive (+) while the other body is negative (-), they are said to have unlike or opposite charges. The law of electric charges may be stated as follows: Like charges repel each other; unlike charges attract each other.
- Fall '18
- Prof Robles
- Basic Electrical Engineering, Electric charge