Module 3: Electrical Fundamentals Topic 3.1: Electron Theory PDF

Module 3: Electrical Fundaments Topic 3.1: Electron Theory  INTRODUCTION On completion of this topic you should be able to: 3.1.1 Define the structure and distribution of electrical charges within: Atoms...

Module 3: Electrical Fundaments Topic 3.1: Electron Theory  INTRODUCTION On completion of this topic you should be able to: 3.1.1 Define the structure and distribution of electrical charges within: Atoms Molecules Ions Compounds 3.1.2 Define the molecular structure of conductors, semiconductors and insulators. 30-03-2024 Slide No. 2  ATOMS Atoms – smallest particles to which elements can be reduced and retains its characteristic. Comprised of: Protons – positively charged Neutrons – neutrally charged Electrons – negatively charged Forces between the so called positive and negative charges are the fundamental cause of electrical phenomena. 30-03-2024 Slide No. 3  MOLECULES Consists of 2 or more atoms bonded together. Smallest particle to which a substance can be reduced and retain its characteristics. This applies to all substances – liquids, solids, and gases. Example - Nicotine C10H14N2 The Nicotine structure includes: 10 Carbon atoms 14 Hydrogen atoms 2 Nitrogen atoms Atom Colour Carbon Green Hydrogen Gray Nitrogen Blue 30-03-2024 Slide No. 4  COMPOUNDS Matter in which all molecules are identical, but molecules are comprised of different atoms in exact proportions. The two or more individual elements combine to form a separate substance whose characteristics may be completely different from the original elements characteristics. Water is a compound: Made up of Hydrogen and Oxygen atoms (H2O). The same is true also of Carbon Dioxide: Carbon and Oxygen atoms (CO2). And also of Common Salt: Sodium and Chloride atoms (NaCl). 30-03-2024 Slide No. 5  IONS Normal atoms have a neutral charge Same number of positively-charged protons as there are negatively-charged electrons An ion is an atom that has lost or gained electrons. Charge will be positive if atom has lost electrons and negative if atom has gained electrons. 30-03-2024 Slide No. 6  STATIC ELECTRICITY Greek philosopher Thales experimented with what came to be called Static Electricity in about 500 BC. Certain materials exert forces on each other which were discovered to be electrical. Rubbing the amber - strips it of electrons making it positive and able to attract a negative substance. Shows amber attracting small feathers. 30-03-2024 Slide No. 7  BENJAMIN FRANKLIN Benjamin Franklin experimented with wet string and a metal key in a thunderstorm! He discovered that energy was transferred from the lightning to the ground, and was the first to use the word current. Energy transfer is now the major use for electricity. 30-03-2024 Slide No. 8  CONDUCTORS AND INSULATORS A balanced atom has an equal number of protons and electrons. Hydrogen – 1 proton, 1 electron. Copper – 29 protons, 29 electrons. Electrostatic attraction holds the electrons in orbit, opposing the centrifugal force. Outermost shell is the Valence shell, and it contains the Valence electrons. Valence Electron 30-03-2024 Slide No. 9  CONDUCTORS AND INSULATORS Outer or valence electrons can be easily forced from their orbits. A positive electrical force will attract and steal electrons from the outer shell. This creates a positively charged ion. Electrons constantly move within a material from one atom to another – free electrons. The motion of free electrons makes up an electric current. The availability of electrons determines whether a material will be: Conductor Semi-conductor Insulator 30-03-2024 Slide No. 10  CONDUCTORS Substances which readily permit the free flow of a large number of electrons are called conductors. A good conductor has 1 – 3 electrons in valence shell: More loosely held in orbit Room for more electrons to join Four good conductors are: Silver Copper Gold Aluminium 30-03-2024 Slide No. 11  INSULATORS Any material that inhibits the flow of electricity is called an insulator. A good insulator has 5 – 8 electrons in valence shell: Solidly held in orbit, will not readily move to another atom No room for more to join Insulators have a high resistivity. Four good insulators are: Glass Rubber Plastic Ceramic 30-03-2024 Slide No. 12  SEMI-CONDUCTORS A semi-conductor has 4 electrons in the valence shell. Silicon and Germanium exist in this configuration, form a crystalline structure and are almost an insulator. Mixing in impurities will produce a semi-conductor. Arsenic incorporates extra electrons – N Type Material. Boron incorporates electron holes – P Type Material. Semi-conductors are the basis of electronic components. No electron in the BORON atom to form a covalent bond Extra electron in the ARSENIC atom creates material with an excess “Electron Hole” Of electrons created 30-03-2024 Slide No. 13  CONCLUSION Now that you have completed this topic, you should be able to: 3.1.1 Define the structure and distribution of electrical charges within: Atoms Molecules Ions Compounds 3.1.2 Describe the molecular structure of conductors, semiconductors and insulators. 30-03-2024 Slide No. 14  This concludes: Module 3: Electrical Fundaments Topic 3.1: Electron Theory