Basic Electrical Engineering - GEC 210 PDF

Faculty of Engineering Baze University Abuja Basic electRICAL engineering GEC 210 Asia’u...

Faculty of Engineering Baze University Abuja Basic electRICAL engineering GEC 210 Asia’u Talatu Belgore Email: asia’[email protected] Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Course Outline Basic Concept of Electricity DC Circuit Analysis AC Circuits DC & AC Machines AC Power Physics of Devices - Insulators, Conductors and Semiconductors Measurement and Instrumentation Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Books for the course ❖Principles and Applications of Electrical Engineering (6th International Edition); Rizzoni, Giorgio; Kearns, James, Published by U.S.A.: McGraw-Hill, 2015 ❖Fundamentals of Electrical Engineering and Electronics; B. L. Theraja, S. Chand Limited, 1 Jun 2006. ❖Electrical Engineering: Principles & Applications (6th Edition), Allan R. Humbly, Pearson; January, 2013. Electrical Engineering Department By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja ASSESSMENT METHOD C.A Exam Total 100% Electrical Engineering Department Lecture 2 - EEE405 4 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Basic Concept of Electricity Electron is assumed to be negatively charged Proton is positively charged Valence shells; 2, 8, 18, 32 Best conductors, copper, silver and gold all with 1 valence electron ©quatr.us Electron Proton Neutron Electrical Engineering Department By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Electricity is a physical phenomena associated with the flow of electric charge/electrons through conductors. It is a form of energy that comes in positive or negative form. Charge is measured in coulombs (C) The charge of an electron (e) is =1.602 × 10−19 C 1 C of charge has 1/1.602 x 10−19 = 6.24 x 1018 electrons Law of Conservation of Charge: “Charge can neither be created nor destroyed, only transferred.” Electrical Engineering Department Lecture 2 - EEE405 6 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Basics of electricity Volts – pressure Amps – flow / current Ohms – resistance These 3 units can be used to measure how much electricity is needed. A german physicist, Mr Georg Ohm invented the Ohm’s Law formula: Electrical Engineering Department Lecture 2 - EEE405 7 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Basic Circuit Laws Ohm’s Law: “The voltage across a resistor is directly proportional to the current flowing through the resistor” Mathematically expressed as R = resistance of the resistor. Resistance is the ability to resist, stop or hinder the flow of current, measured in ohm (Ω) To obey Ohm’s law, current flows from a region of higher potential to a region of lower potential Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja ❖Resistance (R) Unit = ohms Symbol = It depends : i. length of object ii. Cross sectional area i.e inversely proportional iii. Nature of conductor iv. Temperature i.e Electrical Engineering Department Lecture 2 - EEE405 9 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja ❖Resistivity Electrical Engineering Department Lecture 2 - EEE405 10 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja ❖Potential Difference Also known as electric potential (v) Electrical Engineering Department Lecture 2 - EEE405 11 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Voltage (or potential difference): the energy needed to move a unit charge though an element Voltage is measured in volts (v) 1 volt (V) = 1 joule/coulomb represents the voltage between 2 points and in a circuit. It denotes point has a potential of higher than point. Electrical Engineering Department By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja ❖Current Represented as I; unit = amperes; A I= Q/t i.e. rate of flow of charge per unit time Ohms Law Consider a conductor, with resistance R, current flowing through (I), p.d = v Electrical Engineering Department Lecture 2 - EEE405 14 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Current is the rate at which charge flows past a point in a circuit. 1 ampere (A) = 1 coulomb/second (C/s) Two types of current: direct current (DC) and alternating current (AC). DC: current remains constant with time, denoted by I AC: current varies with time, denoted by i Electrical Engineering Department ©physics10aps.blogspot.com.ng/ By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Power is the rate of energy consumption in a circuit Power is measured in watts (W) Positive sign (+) denotes power is absorbed by an element (e.g., resistor, inductor) Negative sign (-) denotes power is supplied by an element (e.g., battery, generator) Electrical Engineering Department By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Signs of power Electrical Engineering Department By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Law of Conservation of Energy: “Energy can neither be created nor destroyed, only transferred” Hence, the algebraic sum of power in a circuit, at any given time is equal to zero. The total power supplied to the circuit must balance the total power absorbed. Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Example : A copper wire has a length of 160cm and a diameter of 1.00 mm. If the wire is connected to a 1.5-volt battery, how much current flows through the wire? Resistivity for copper is 1.72X 10^-8Ωm. Electrical Engineering Department Lecture 2 - EEE405 19 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja ❖What is a circuit? An electric circuit is an interconnection of electric elements. ❖Types of elements: Passive and Active Passive elements is an electrical component that does not generate power but instead receive energy (absorb) and then convert it heat or store and/or release it. Examples; resistors, capacitors and coils(inductors). Active elements supply energy to the circuit. E.g., voltage and current sources, generators etc. Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Voltage and current sources can be grouped into: independent and dependent sources Independent source: Active element that provides voltage or current that is completely independent of other sources Dependent source: Active element source that is controlled by other voltage or current sources. Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Voltage source A. ideal voltage source VL is not dependent on IL characteristics Electrical Engineering Department Lecture 2 - EEE405 22 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Current source A. Ideal current source B. Practical current source Electrical Engineering Department Lecture 2 - EEE405 23 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Resistance in series Resistors in series are joined end-to-end in a circuit The equivalent resistance is equal to the summation of all the resistances Note: Same current flows throughout the circuit Resistors have individual voltage drops Voltage drops are additive Applied voltage is equal to the sum of individual voltage drops Resistances are additive Powers are additive Electrical Engineering Department Lecture 2 - EEE405 24 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Resistance in series Example: Current passing through the circuit is the same. Electrical Engineering Department Lecture 2 - EEE405 25 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Resistance in parallel / shunt Two or more elements are in parallel if they are connected to the same two nodes. Potential difference across all resistances is the same Current in each resistor is different and follows Ohm’s Law Total current is the sum of the individual currents Electrical Engineering Department Lecture 2 - EEE405 26 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Resistances in parallel Consider the following circuit: Electrical Engineering Department Lecture 2 - EEE405 27 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja The equivalent resistance of 2 resistance in parallel is the product of both resistance divided by their sum. Electrical Engineering Department Lecture 2 - EEE405 28 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Definitions Branch: Represents a single element such as a voltage source, current source or a resistor. It represents any two-terminal element. Node: The point of connection between two or more branches. It is normally represented by a dot in a circuit. Note: A short circuit (a connecting wire) with two nodes becomes a single node Loop: Any closed path in a circuit. It starts at a node and passes through a set of nodes and returns to the starting node without passing through any node more than once. Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja A loop is independent i it contains a branch that is not inside any other loop. Mesh: A loop that contains no other loop within it (Independent loop). A network with b branches, n nodes, and l independent loops will satisfy the fundamental theorem of network topology: Electrical Engineering Department By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Kirchhoff's current law (kcl) Statement: the sum of currents flowing towards a node is equal to the sum of currents flowing away from the node. (i.e. incoming = outgoing) Electrical Engineering Department Lecture 2 - EEE405 32 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Kirchhoff's voltage law (kvl) Signs to follow while applying KVL: Electrical Engineering Department Lecture 2 - EEE405 33 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Voltage Sign Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Statement: The algebraic sum of the product of current and resistance of various branches of closed loop of circuit, plus the algebraic sum of the emf’s in that closed loop is equal to zero. ❑The algebraic sum of all voltages around a closed path (or loop) is zero” ❑Or, “Sum of voltage drops = Sum of voltage rises. Anti-clockwise: Clockwise: Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Voltage division rule Used to determine what portion of voltage will drop across each of the resistors when the resistors are connected in series. Since it is a series circuit, current throughout the circuit remains the same. Consider the following circuit: Electrical Engineering Department Lecture 2 - EEE405 36 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja To find the voltage across R1 & R2: Electrical Engineering Department Lecture 2 - EEE405 37 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Electrical Engineering Department Lecture 2 - EEE405 38 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Current division rule In a parallel resistance circuits, voltage drop across each resistor is the same as the supply voltage but current varies. Current divider rule is used to find individual currents in a parallel resistance circuit. Consider the circuit below: Electrical Engineering Department Lecture 2 - EEE405 39 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Electrical Engineering Department Lecture 2 - EEE405 40 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Electrical Engineering Department Lecture 2 - EEE405 41 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Examples: 1. Find the value of resistor (R), when the power consumed by the 12ohm resistor in the given circuit is 36w. Electrical Engineering Department Lecture 2 - EEE405 42 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Given: Electrical Engineering Department Lecture 2 - EEE405 43 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Recall that V= I x R Electrical Engineering Department Lecture 2 - EEE405 44 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Electrical Engineering Department Lecture 2 - EEE405 45 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja 2. Calculate the current and power in the circuit below: Electrical Engineering Department Lecture 2 - EEE405 46 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja 3. Voltage divider example: consider the circuit below: Electrical Engineering Department Lecture 2 - EEE405 47 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Electrical Engineering Department Lecture 2 - EEE405 48 By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Concept check!!! Students should have good understanding on the basics of electricity Good understanding of the basic principles: current, voltage, resistance, conductance, resistivity, ohms law etc. Good understanding on principle of voltage and current source (ideal and practical) Resistance in series and parallel (shunt) and corresponding circuit calculations. Concept of KCL and KVL, as well as worked examples Concept of current and voltage division rule. Electrical Engineering Department Lecture 2 - EEE405 49 By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Circuit Analysis Solving Simultaneous Equations Electrical Engineering Department By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Electrical Engineering Department By Abdullahi Yusuf Sada Faculty of Engineering Baze University Abuja Electrical Engineering Department By Abdullahi Yusuf Sada  Faculty of Engineering Baze University Abuja Example: solve the following equation: Electrical Engineering Department Lecture 2 - EEE405 53 By Abdullahi Yusuf Sada