Emirates Aviation University Electrical Fundamentals PDF

Module 3: Electrical Fundamentals Topic 3.3: Electrical Terminology  INTRODUCTION On completion of this topic you should be able to: 3.3.1 Describe the following terms, their units and factors affecting them: Potential differ...

Module 3: Electrical Fundamentals Topic 3.3: Electrical Terminology  INTRODUCTION On completion of this topic you should be able to: 3.3.1 Describe the following terms, their units and factors affecting them: Potential difference Electromotive force Voltage Current Resistance Conductance Charge Conventional current flow Electron flow 30-03-2024 Slide No. 2  CHARGE Coulomb – unit for quantities of electric charge (electrons) transferred between points of different electrical potential. 1 Coulomb = 6.24 x 1018 electrons C – symbol for Coulombs Q – symbol for charge Q=3C means a charge of 3 Coulombs 30-03-2024 Slide No. 3  CURRENT Transfer of electrons between points of different potential at varying rates of flow. Rate of transfer is measured in Coulombs per second. One (1) Coulomb per second is one (1) Ampere. Ampere - unit of current - Amp A – symbol for Amperes I – symbol for current I=3A means a current of 3 Amps 30-03-2024 Slide No. 4  CURRENT FLOW CONVENTIONS Electron Conventional Current Flow Current Flow Electricity was used before the atom was fully understood. Assumed that (like water) charges move from high (+) to low pressure (-). Known as Conventional Current Flow (+ve to –ve). Current flow is actually flow of electrons (–ve to +ve) – Electron Flow. 30-03-2024 Slide No. 5  ELECTROMOTIVE FORCE / VOLTAGE EMF is the energy that makes electrons move Measure of energy applied to electrons to remove and propel them from their orbits. EMF is what makes current flow. Current in a circuit is proportional to the voltage driving/forcing it through the circuit. Doubling the voltage, doubles the current and halving the voltage, halves the current. Volt is the unit of EMF or voltage. V is the symbol for Volts. E is the symbol for EMF. Example: E = 3 V means an EMF of 3 Volts. 30-03-2024 Slide No. 6  VOLTAGE Both Electromotive Force and Potential Difference are methods of expressing the energy to move an electron from one place to another. Voltage is the number of Joules of energy available per Coulomb of electrons. Hence the expression "Potential" as in Potential Energy; the potential to do work. 30-03-2024 Slide No. 7  POTENTIAL DIFFERENCE 0 100 +100 PD = Volts Volts Volts -100 100 0 PD = Volts Volts Volts -100 100 0 100 +100 Volts Volts Volts Volts Volts 200 PD = Volts Potential is with reference to a point (eg. +100 Volts with reference to 0 Volts). PD – Voltage difference between 2 bodies - measured in Volts. 30-03-2024 Slide No. 8  POTENTIAL DIFFERENCE 5 25 +30 PD = Volts Volts Volts -30 35 5 PD = Volts Volts Volts -30 35 5 25 +30 Volts Volts Volts Volts Volts 60 PD = Volts Potential is with reference to a point (eg. +100 Volts with reference to 0 Volts). PD – Voltage difference between 2 bodies - measured in Volts. 30-03-2024 Slide No. 9  RESISTANCE Resistance – electrical resistance to current flow. Current in a circuit is inversely proportional to resistance of circuit. Doubling resistance, halves current and halving resistance, doubles current. Directly proportional to length of conductor. Inversely proportional to cross-sectional area of conductor. Ohm is the unit of electrical resistance Ω is the symbol for Ohms R is the symbol for resistance Example: R = 3 Ω means a resistance of 3 Ohms 30-03-2024 Slide No. 10  FACTORS AFFECTING RESISTANCE Conductors Insulators 1-3 electrons 5-8 electrons in outer ring in outer ring Resistance of any object depends upon 4 factors: Material from which it is made Length Cross-sectional area Temperature For most materials: Hotter the material – the higher the resistance to current flow Colder the material – the lower the resistance to current flow 30-03-2024 Slide No. 11  CONDUCTANCE Siemens (mhos) = 1 R Conductance is the reciprocal of resistance. Used to be known as a mho (ohm spelt backwards). Rarely used term. Siemen - unit for measurement of a material’s ability to conduct current. S – symbol for Siemens G – symbol for conductance G=3S means a conductance of 3 Siemens 30-03-2024 Slide No. 12  CONCLUSION Now that you have completed this topic, you should be able to: 3.3.1 Describe the following terms, their units and factors affecting them: Potential difference Electromotive force Voltage Current Resistance Conductance Charge Conventional current flow Electron flow 30-03-2024 Slide No. 13  This concludes: Module 3: Electrical Fundamentals Topic 3.3: Electrical Terminology