Basic Electrical and Electronics Engineering Unit 1 PDF

uNIT-1 BASIC ELECTRICAL AND ELECTRONICS ENGINEERING ECE-249 1 Contents Basic Terminology Charge Current Voltage Power Energy Basic Circuit Elements Active Elements and Passive Elements Lin...

uNIT-1 BASIC ELECTRICAL AND ELECTRONICS ENGINEERING ECE-249 1 Contents Basic Terminology Charge Current Voltage Power Energy Basic Circuit Elements Active Elements and Passive Elements Linear Elements and Non-linear Elements Bilateral Elements and Unilateral Elements Resistors Capacitors Inductors 2 Introduction In modern life, circuits are everywhere. Without circuits you wouldn't have indoor lights you wouldn't have the computer you wouldn't have anything that is powered by electricity 3 Electric charge Electric charge : The most basic quantity in an electric circuit is the electric charge. charge is defined excess or deficiency of electron charge can be positive or negative materials with an excess of electrons are negatively charged and with a deficiency of electrons are positively charged. measured in coulombs (C) symbol: Q or q the smallest charge, the electronic charge, is carried by an electron is 4 Electric current Electric current : Current is the rate of charge flow The unit of current is the ampere (A) and corresponds to the quantity of total charge that passes through an arbitrary cross section of a conducting material per unit second. Mathematically, Where Q is the symbol of charge measured in Coulombs (C), I is the current in amperes (A) and t is the time in second (s). 5 Electric current Two types of current: A direct current (DC) is a current that remains constant with time and denoted by symbol I. An alternating current (AC) is a current that varies with time and represented by the symbol or (i ). 6 Voltage Voltage : To move the electron in a conductor in a particular direction requires some work or energy transfer. This work is performed by an external electromotive force (emf), typically represented by the battery. Potential difference:The difference of potential or voltage or emf across the two points of the conductor, which makes the current to flow, is know as potential difference, measured in volts (V). One point has a higher potential and the other points have lower potential. Voltage : Work done per unit charge V=W/Q Where, W is the work done in Joule, Q is the charge and its unit is Coulomb. 7 Electrical Power and Electrical Energy The rate at which work is done in an electric circuit is known as electric power. Workdonein electric circuit W Power =  P= Time t As we know, Q W I=  Q = It and V =  W = VQ t Q 2 W = VIt V P = VI = I 2 R = W VIt R P= =  P = VI t t The total work done in an electric circuit is known as electric energy. Electrical energy ,W = Electric power  time 2 V W = Pt = VIt = I 2 Rt = t R 8 Conti… The unit of electric power is joule/sec or watt. The unit of electrical energy is kilowatt hour (kWh) When the current enters the positive terminal, p = +iv power is absorbed (acts as sink) When the current leaves the positive terminal, p = −iv power is delivered ( act as source) 9 Basic Circuit Elements Circuit Elements: An element is the basic building block of a circuit. An electric circuit is simply an interconnection of the elements. Circuit analysis: is the process of determining voltages across (or the currents through) the elements of the circuit. A) Active elements: The elements which are capable of generating or delivering the energy are called active elements. E.g., Generators, Batteries B) Passive element : The elements which are capable of receiving the energy are called passive elements. It can’t deliver power (energy) to other elements E.g., Resistors, Capacitors and Inductors 10 Linear and non-linear Element A linear element is one whose parameters are constant with the time also they do not change with voltage or current & circuit follows Ohm’s Law. V-I characteristics of a linear circuit is a straight line. Examples: Resistors, capacitors, Transformers, and Inductors are Linear components. Non-linear element is one whose parameters vary with the time and change with voltage and current and also they don’t follow the Ohm’s Law. V-I characteristics of the non-Linear circuit is Not a straight line. Exapmles: Transistor, Diodes are Non -Linear elements. 11 Unilateral and Bilateral Elements Unidirectional elements are those which allow the flow of current through them in one direction only.. PN Junction Diode is the best example of Unidirectional Element Bidirectional elements are those which allow the flow of current through them in both directions. A resistor is the best example of Bidirectional Element 12 Resistor Resistance (also known as ohmic resistance or electrical resistance) is a measure of the opposition to current flow in an electrical circuit. Resistance is measured in ohms, symbolized by the Greek letter omega (Ω). The circuit element used to model the current resisting behavior of a material is called the resistor. The resistance of a resistor depends on the material of which the conductor is made and geometrical shape of the conductor. The resistance of a conductor is proportional to the its length (l) and inversely proportional to its cross sectional area (A). Where, ρ is the resistivity and its value depends on the material of which the conductor is made. The reciprocal of resistance is called conductance G. The unit of resistance is ohm and the unit of conductance is mho or Siemens. 13 14 Resistor in series and parallel Resistor in series and parallel Resistor in series and parallel Resistor in series and parallel SERIES CONNECTIONS SERIES CONNECTION: Two or more elements are in series if they exclusively share a single node and consequently carry the same current. Point to Remember for Series Circuits PARALLEL CONNECTIONS PARALLEL CONNECTION: Two or more elements are in parallel if they are connected to the same two nodes and consequently have the same voltage across them Question 2. Calculate the total resistance between the points A and B. a) 7 ohm b) 0 ohm c) 7.67 ohm d) 0.48 ohm 23 Question 1 ohm in parallel with 2 ohm give 2/3 ohm equivalent which is in series with 4 ohm and 3 ohm so total resistance between A and B = 4 + 2/3 + 3 = 23/3 = 7.67 ohm. 24 Question 25 Answer 26 Inductance The induced emf across a coil is directly proportional to the rate of change of current through it. The proportionality constant in that relation is known as inductance. Inductor works under AC power source; it creates short circuit path to the DC power source 27 Inductor in series By using Kirchoff’s voltage law 28 Inductor in parallel 29