Note for ELECTRIC CIRCUITS - EC By JNTU Heroes

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LECTURE NOTES ON ELECTRICAL CIRCUITS II B.Tech I semester Electrical and Electronics Engineering 1

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Contents To Be Covered UNIT-I Circuit concepts, RLC parameters, voltage and current sources, independent and dependent sources, source transformation, voltage-current relations for passive elements, kirchoff’s laws , network reduction techniques, nodal analysis, mesh analysis, super nodal and super mesh analysis. UNIT-II RMS, average ,peak and form factor of sinusoidal wave form, steady state analysis of R,L,C in series and parallel combinations with sinusoidal excitation,concept of reactance , impedance, admittance and susceptance, real,reactive and apparent powers and complex power. UNIT-III Locus diagrams for all series and paralle combinations of RLC parameters, resonance of series and parallel circuits, concept of bandwidth and q factor. Magnetic circuit, faradays laws of electro-magnetic induction, concept of self and mutual induction, dot convention, co-efficient of coupling, composite magnetic circuit, analysis of series and parallel magnetic circuits. UNITDefinitions, graph, tree, co-tree, cutest, tie-set, matrices for planar networks, loop and nodal IV methods for analysis of networks with dependent and independent voltage and current sources, duality and dual networks UNIT-V Network theorems with DC and ACnexcitations,tellegen’s,compensation,thevenin’s, nortan’s, milliman’s, reciprocity and super-position theorems. 2

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UNIT-I 1.1 INTRODUCTION: With increase in population the need for electricity also increases therefore it is necessary to rise number of electrical engineers. The electrical engineering mainly deals with generation , transmission and distribution of electricity. Electrical circuits is the basic and fundamental subject which lays path to understand subjects related to generation , transmission and distribution of electricity. In the first unit we shall deal with what is electrical circuit and formation of electrical circuit. Knowing or unknowing we come across electron in our life daily, studying the properties of these electrons leads to the terms voltage, current and power. Hence the basic definitions of voltage , current , power and energy are studied here. 1.2 CIRCUIT: The electrical circuit consists of mainly three parts , they are -- source, connecting wire and load or sink. Source : An source may be battery which forces electrons into the circuit. Connecting wire : This is part which provides path for electrons to flow. Load : The load may be bulb etc. when electrons flow through it an reaches the Source it glows . If the electrons are provided closed path to flow, leads to current is called as electrical circuit. 1.3 BASIC DEFINITIONS: Voltage(V) : The potential difference between force applied to two oppositely charged particels to bring them as near as possible is called as potential difference .( in electrical terminology it s voltage). V = W / Q (v) υ = dw / dq (v) v- volts , units of voltage. Unit volt is defined as 1C of charge developed when 1 J of energy is applied. Current(I) : The flow of electrons develops the current. I = Q/ t (A) i = dq / dt (A) A = Ampere, units of current. - Unit ampere of cuurent is constituted when 1C of charge is flowing in 1S. 3

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Power(P): It is defined as product of volateg and power in electrical circuits or Rate of change of energy. P = dw/dt = dw/ dq . dq/dt = υ .i (W) W = watts, units of power. Unit watt is the 1J of energy is dissipated in 1S. Enegy : It is the capacity to do work or it is defined as power consumed over Given interval of time.(w) W = ʃ P dt.(J) J = Joules, units of energy 1J = 1 watt-sec. 1.3 BASIC PARAMETERS: Any electrical mainly consists of three important elements , they are resistor, inductor and capacitor. Let us deal these parameters in detailo. 1.3.1 Resistor: resistor is the element which restricts flow of electrons and this Property of opposing electrons is called as resistance. OHM’s Law : ohm’s law states that current flowing through circuit is Directly proportional to potential difference applied. ( at constant temperature) I α V, at constant T. I.R = V. R = V / I, hence resistance can be calculated as ratio of Volatge to current in any element or circuit. = OHMS ῼ, units of resistance. R= 1.3.2 Inductor: An length of wire twisted forms the basic inductor.(L). when Alternating curent is allowed through such a element it induces Voltage in it. e, ɸ 4