UNIT-I1. DEFINE CURRENT? Current is defined as the rate of flow of charge (free electrons).Current is represented by I and its unit is Ampere. 2. DEFINE VOLTAGE? Voltage is defined as the potential difference between ends of the conductor. Voltage is represented by V and its unit is Volts. 3. STATE OHM’S LAW? It states that the voltage across the resistor is directly proportional to the current flowing through the resistor. V=I*R 4. DEFINE POWER? Power is define as rate of doing work and its unit is Watt or Joule/sec. (Or) It is the product of current and voltage P=V*I 5. STATE KIRCHOFF’S CURRENT LAW? It states that algebraic sum of the currents meeting at any junction is zero. (Or) It can be also stated that sum of current entering the junction is equal to the sum of current leaving the junction. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 1 6. STATE KIRCHOFF’S VOLTAGE LAW? It states that in a closed circuit the algebraic sum of product of the current and resistance of all the elements plus the algebraic sum of the EMF induced in the circuit is equal to zero. ΣIR+ ΣEMF=0 (OR) It can be stated that the sum of the voltage drops is equal to the sum of voltage drop. 7. DEFINE ACTIVE ELEMENT? Active element is defined as the energy sources. It can be either voltage or current sources. Example: Transistor. 8. DEFINE PASSIVE ELEMENT? Passive element is defined as the one which dissipates energy in form of heat or which stores energy. Example: resistance, inductance. 9. DEFINE NETWORK? Interconnections of circuit elements are called network. 10. DEFINE CIRCUITS? A Network that contains at least one closed path is known as circuits. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 2 11. WHAT IS MEAN BE LUMPED PARAMETER NETWORK? A network consisting of physically separated elements such as resistor, capacitor is known as lumped parameter network. Example: RLC network. 12. DEFINE DISTRIBUTED PARAMETER NETWORK? A network consisting of elements that are not separable for analytical purpose is known as distributed network. Example: Transmission line. 13. DEFINE BRANCH? A branch is a portion of a circuit with two terminals connected to it. 14. DEFINE NODE? A node is a junction of two or more points. It is a point at which two or more circuit elements are connected. 15. DEFINE LOOP? A loop is any closed connections of branches. 16. WHAT ARE UNILATERAL AND BILATERAL NETWORKS? BILATERAL NETWORKS: A Circuit whose characteristics, behavior is same irrespective of the direction of current through various elements is called unilateral network. Example: resistor consists of resistor alone. UNILATERAL NETWORKS: A Circuit whose characteristics, behavior is dependent on the direction of current through various elements is called unilateral network. Example: diode. 17. WHAT ARE LINEAR AND NON-LINAER NETWORK? LINEAR NETWORK: A circuit or network whose parameters I.e elements like resistance, inductance, capacitance are always constant irrespective of change in time, voltage, temperature. Ohm’s law can be applied to such network. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 3 NON-LINAER NETWORK: A circuit or network whose parameters I.e elements like resistance, inductance, capacitance change their values with change in time, voltage, temperature. Ohm’s law can be applied to such network. 18. DEFINE GRAPH? When all elements in a network are replaced by lines with circles of dots at both ends. 19. DEFINE TREE? It is an interconnected open set of branches which includes all the nodes of the given graph. 20. DEFINE IMPEDANCE AND ADMITTANCE? Impedance: The ratio of phasor voltage to phasor current is called impedance Z=V/I. Admittance: reciprocal of impedance is called admittance (Y) Y=I/Z. 21. DEFINE DUALITY? In an electrical circuit itself there are pair of terms, which can be interchanged to get new circuits. 22. WHAT IS AN ORIENTED GRAPHS? A directed graph is called an oriented graph if it is the orientation of an undirected graph. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 4 UNIT –II NETWORK THEOREMS FOR AC AND DC CIRCUITS 1. STATE SUPERPOSITION THEOREM? In a linear bilateral network containing two or more independent sources, the voltage across or the current through any branch is algebraic sum of individual voltages or currents produced by each independent source acting separately with all the independent sources set equal to zero. 2. STATE RECIPROCITY THEOREM? In any passive, linear, bilateral, single source network interchanging the position of ideal voltage source and an ideal ammeter does not alter the ammeter reading (current) and interchanging the position of current source and an ideal voltmeter does not alter voltmeter reading (voltage). 3. STATE THEVENIN’S THEOREM? Any linear active two terminal network containing resistance and voltage sources and or current sources can be replaced by a single voltage sources Vth in series with a single resistance Rth. The thevenin equivalent voltage Vth is the open circuit voltage at the network terminals, and the thevenin’s resistance Rth is the resistance between the network terminals when all sources are replaced with their internal resistances. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 5 4. STATE NORTON’S THEOREM? Any linear active two terminals network containing resistance and voltage sources and or current sources can be replaced by single current source IN in parallel with a single resistance RN. The Norton’s equivalent current IN is the short circuit current through the terminals. RN- resistance between the network terminals when all sources are replaced with their internal resistances. 5.STATE MAXIMUM POWER TRANSFER THEOREM? In a linear bilateral network containing an independent voltage source in series with resistance Rs delivers maximum power to the load resistance RL when RL = Rs. Similarly the independent current source in parallel with source resistance R s delivers a maximum power to the load resistance when RL = Rs. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 6 5. STATE COMPENSATION THEOREM? In a linear network any resistance R that carries a current I can be replaced by a voltage source with emf V=IR with zero internal resistance. Similarly if the voltage across the resistance is V then it can be replaced by a current source I=V/R after replacement the current and voltages in all the other parts of the network remain unchanged. 6. STATE MILLMAN’S THEOREM? Consider N voltage sources V1, V2, -------VN in series with N resistors R1, R2, ------RN. Then according to Millman’s theorem we can replace all the voltage sources and resistance between terminals by a single voltage source V in series with a single resistance R. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 7 1/R = G 7. STATE MAXIMUM POWER TRANSFER THEOREM? (AC CIRCUIT) Maximum power will be delivered from a source to a load, when the load impedance is equal to the complex conjugate of the internal source impedance. 8. STATE MILLMAN’S THEOREM? (AC CIRCUITS) In any network, if the voltages V1, V2………. Vn with internal impedances Z1, Z2 …..Zn respectively, is in parallel then these sources may be replaced by a single voltage source V in series with single impedance Z. 9. STATE TELLEGEN’S THEOREM? In any network, the summation of instantaneous power or the summation of complex power of sinusoidal sources is zero. 10. WRITE THE EQUATION FOR CONVERTING DELTA TO STAR? ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 8 11. WRITE THE EQUATION ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR FOR CONVERTING STAR TO DELTA? 9 UNIT-III COUPLED CIRCUITS, RESONANCE AND THREE PHASE CIRCUITS: 1. DEFINE RESONANCE? An AC circuit is said to in resonance when the input voltage and input current are in phase. At Resonance the power factor of the circuit is unity and the circuit is purely resistive. 2. WHAT IS THE CONDITION FOR SERIES RESONANCE? XL=XC If inductive reactance of a network equals capacitive reactance then the network is said to be in resonance. 3. WHAT IS RESONANT FREQUENCY? The frequency at which resonance occurs is called resonance frequency. 4. WHAT ARE THE APPLICATIONS OF SERIES RESONANCE? a) It is used to increase the signal voltage and current at desired frequency. b) Used in some electronic circuits such as antenna circuits and tuning circuits. 5. DEFINE BANDWIDTH? Bandwidth is defined as the band frequency between upper cut-off frequency (f2) and lower cut-off frequency (f1). BANDWIDTH= f2-f1 = R/2ΠL. 6. DEFINE QUALITY FACTOR OR Q-FACTOR? The quality factor is defined as the ratio of maximum energy stored to the energy dissipated per cycle. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 10 It is also defined as ratio of bandwidth to the resonant frequency. B= BANDWIDTH 7. DEFINE HALF POWER FREQUENCIES? The frequencies at which the power is half the power at resonance are called half power frequencies. LOWER HALF POWER FREQUENCY f1 = f0 – R/4ΠL UPPER HALF POWER FREQUENCY f2 = f0 + R/4ΠL. 8. WRITE THE CONDITION AT WHICH A PARALLEL RESONANCE CIRCUITRESONATES AT ALL FREQUENCIES? R1=R2= 9. DEFINE SELF INDUCTANCE? It is defined as flux linkage in that coil per one ampere current in the same coil. LN B I It also defined as Weber turns per ampere current in the coil. Unit is Henry. 10. DEFINE MUTUAL INDUCTANCE? The mutual inductance between 2 coils is defined as Weber turns in one coil per ampere current in other coil. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 11 It is also defined as the ability of one coil to produce emf in other coil by induction when the current in the first changes. 11. DEFINE COEFFICIENT OF COUPLING (K)? The fraction of the total flux produced by coil1 linking coil 2 is called of coefficient of coupling. 12. WRITE THE RELATION BETWEEN M, K, L1 AND L2? 13. STATE DOT RULE? If both currents enter dotted ends of couple coils or if both currents leave dotted ends then the signs on the M-terms will be same as the signs on the L-terms. If one current enters a dotted end and other an un-dotted end, then the signs on the M-terms will be opposite to the signs on the L-terms. 14. WHAT IS SERIES AIDING CIRCUIT? When the current enters both the coils at dotted terminal in a series circuit then it is called as series aiding. LEFF = L1+L2+2M. 15. WHAT IS SERIES OPPOSING CIRCUIT? When the current enters the first coil at dotted terminal and leaves the other coil at dotted terminal in a series circuit then it is called as series aiding. LEFF = L1+L2-2M. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 12 16. WHAT IS PARALLEL AIDING CIRCUIT? When the current enters both the coils at dotted terminal in a parallel circuit, then it is called parallel aiding circuit. LEFF = L1L2-M2 L1+L2-2M 17. WHAT IS PARALLEL OPPOSING CIRCUIT? When the current enters the first coil at dotted terminal and leaves the other coil at dotted terminal in a parallel circuit then it is called as series aiding. LEFF = L1L2-M2 L1+L2-2M 18. DEFINE REAL POWER? Real power is defined as the actual power consumed in AC circuit. It is denoted by P. Unit is Watts P=V I COSɸ V= RMS VALUE OF VOLTAGE I= RMS VALUE OF CURRENT ɸ= PHASE ANGLE BETWEEN V&I. 19. DEFINE REACTIVE POWER? Reactive power is defined as the total power consumed by pure reactance (either inductive or capacitive or both) in the AC circuit. It is denoted by Q. Its unit is volt Ampere reactive (VAR). Q=V*I Sin ɸ V= RMS VALUE OF VOLTAGE I= RMS VALUE OF CURRENT ɸ= PHASE ANGLE BETWEEN V&I. 20. DEFINE APPARENT POWER? Apparent power is defined as the total power consumed in the AC circuit. It is given by sum of real power and reactive power. It is denoted by S. Its unit is volt . S=P+jQ or S=VI V= RMS VALUE OF VOLTAGE I= RMS VALUE OF CURRENT. 21. DEFINE POWER FACTOR? ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 13 Power factor is defined as the cosine of the angle between the input voltage and input current. P.F = COSɸ. (OR) It is defined as the ratio of real power to apparent power P.F = REAL POWER APPARENT POWER 22. WHAT ARE LINE AND PHASE VOLTAGES AND WHAT IS THE RELATION BETWEEN THEM? Line voltage is defined as the voltage between any two lines of a 3 phase system. It is represented by EL. Phase voltage is defined as the voltage between one line and the neutral wire of the star connected system. 23. WHAT IS THE DIFFERENCEE BETWEEN SINGLE PHASE AND THREE PHASE AC SUPPLY? S.NO SINGLE PHASE AC SUPPLY THREE PHASE AC SUPPLY 1 It has one conductor It has three conductors 2 Low power applications High power applications 3 It has 2 line phases and neutral It has three or four lines. line for return path R, Y, B , N(neutral) ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 14 UNIT –IV TRANSIENT ANALYSIS: 1. WHAT IS TRANSIENT? Transient is a short lived oscillations in a network caused by sudden change of voltage or current or energy storage elements such as inductance and capacitance. 2. WHAT IS TRANSIENT STATE? The behavior of the voltage or current when it is changed from one state to another state is called transient state. 3. WHAT IS TRANSIENT TIME? The time taken for the circuit to change from one steady state to another steady state is called transient time. 4. WHAT IS TRANSIENT RESPONSE? The storage elements deliver their energy to the resistance, hence the response changes with time and get saturated after sometime is referred as transient response. 5. WHAT IS NATURAL RESPONSE? The response of the circuit due to stored energy alone without external source is called natural response. 6. WHAT IS FORCED RESPONSE? The response of the circuit due to without external source is called forced response. 7. WHAT IS TOTAL RESPONSE? TOTAL RESPONSE = NATURAL RESPONSE + FORCED RESPONSE. 8. DEFINE TIME CONSTANT OF RL CIRCUIT? The time taken to reach 63.2% of final value in a RL circuit is called time constant of RL circuit. Time constant T= L/R ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 15 9. DEFINE TIME CONSTANT OF RC CIRCUIT? The time taken to reach 36.8% of initial current in a RC circuit is called time constant of RC circuit. Time constant λ= RC. 10. DEFINE INITIAL VALUE THEOREM? If f(t) and f’(t) both are laplace transformable. 11. DEFINE FINAL VALUE THEOREM? If f (t) and f’ (t) both are Laplace transformable. 12. WHAT ARE THE ADVANTAGES OF LAPLACE TRANSFORM? It transforms the exponential and trigonometric functions into simple algebraic functions. a) It transforms differentiation and integration into multiplication an division. b) It transforms integro-differential equations into algebraic equations. c) It makes use of step and impulse response. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 16 UNIT –V NETWORK FUNCTIONS AND PARAMETERS 1. WHAT IS TRANSFER FUNCTION OF A CIRCUIT? The transfer function of a circuit is defined as the ratio of laplace transform of the output to the laplace transform of the input with the initial conditions are zero. 2. DEFINE POLES AND ZEROS OF A NETWORK? The values of s at which the network function become zero are known as zeros. The values of s at which the network function become infinity are known as poles. 3. DEFINE DRIVING POINT IMPEDANCE? It is defined as the ratio of voltage transform to the current transform at a given port for a network with zero initial conditions. 4. DEFINE DRIVING POINT ADMITTANCE? It is defined as the ratio of current transform to the voltage transform at a given port for a network with zero initial conditions. 5. DEFINE VOLTAGE TRANSFER RATIO? The ratio of output port voltage to input port voltage known as voltage transfer ratio. G(s) = V2(S) V1(S) 6. DEFINE TRANSFER IMPEDANCE? The ratio of output voltage to input current is called transfer function. Z11(s) = V2(S) I1(S) ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 17 7. DEFINE TRANSFER CURRENT RATIO? The ratio of output current to the input current is called transfer current ratio. α21(s) = I (S) 2 I1(S) 8. DEFINE TRANSFER ADMITTANCE? The ratio of output current to the input voltage known as transfer admittance.\ Y 11(s) = I2(S) V1(S) 9. WHAT ARE TWO PORT NETWORK? A network that has two pairs of terminals is called two port networks. 10. WHAT IS ONE PORT NETWORK? A network has a pair of terminals is called one port network. ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 18 11. DEFINE Z PARAMETERS? It is also called as open circuit impedance parameters 12. DEFINE Y PARAMETER? It is also short circuit admittance parameter 13. DEFINE H-PARAMETER? Used for constructing models for transistor 14. DEFINE ABCD PARAMETER It is also called as transmission parameters ELECTRIC CIRCUIT ANALYSIS-PART A PREPARED BY N.SHANKAR 19