Gateway to success. Website:- Helpline no Important Quantities. kg (kilogram) Nm (newton metre) Electrical Quantities

Transcription

1 Gateway to success Subject:-BASIC NETWORK Branch:-EE/EC Website:- Helpline no Important Quantities General Quantities Acceleration, linear Area Energy or work Force Length Mass Power Pressure Temperature value Time Torque Velocity, angular Velocity, linear Volume Wavelength Electrical Quantities Admittance Charge (quantity) Conductance Current Current density Electromotive force (emf) Frequency Impedance Period Potential difference (p.d.) Power, active Power, apparent Power, reactive Reactance Resistance Resistivity Time constant Symbol a A W F l m P p θ t T ω v or u V λ Symbol Y Q G I J E f Z T V P S Q X R ρ Unit m/s 2 (metre/second/second) m 2 (square metre) J (joule) N (newton) m (meter) kg (kilogram) W (watt) Pa (pascal) K or C (Kelvin or degree Celsius) s (second) Nm (newton metre) rad/s (radian/second) m/s (metre/second) m 3 (cubic metre) m meter Unit Ω(ohm) C (coulomb) S (siemen) A (ampere) A/m 2 (ampere/square metre) V (volts) Hz (hertz) Ω (ohm) s (second) V (volt) W (watt) VA (volt ampere) VAr (volt ampere reactive) Ω (ohm) Ω (ohm) Ωm (ohm metre) s (second)

2 Electrostatic Quantities Capacitance Field strength Flux Flux density Permittivity, absolute General Quantities Permittivity, relative Field strength Electromagnetic Quantities Field strength Flux Flux density Inductance, mutual Inductance, self Magneto motive force (mmf) Permeability, absolute Permeability, relative Permeability, of free space Reluctance Symbol C E Ψ D ε Symbol ε r ε 0 Symbol H Φ B M L F μ μ r μ 0 S Unit F (farad) V/m (volt/metre) C (coulomb) C/m 2 (coulomb/square metre) F/m (farad/metre) Unit no units F/m (farad/metre) Unit At/m (ampere turn/metre) Wb (weber) T (tesla) H (henry) H (henry) A/t (ampere-turn) H/m (henry/metre) no units H/m (henry/metre) At/Wb (ampere turn/weber) Electric current:-electric current is the time rate of change of charge, measured in amperes (A). Where current is measured in amperes (A) and 1 ampere = 1 coulomb/second The charge transferred between time t 1 and t 2 is obtained by:- Voltage:-This emf is also known as voltage or potential difference. POWER AND ENERGY:- Power is the time rate of expending or absorbing energy, measured in watts (W). KVL (Kirchhoff s Voltage Law):- KVL states that algebraic sum of voltages in a loop is zero.

3 Or This works on the principle law of conservation of energy. A. Applicable for planner or linear circuit only. B. Applicable for AC and DC both circuits. Nodal Analysis:-Nodal analysis is application of KCL and applicable for both planner and non-planner networks. Mesh analysis:-mesh analysis is nothing but loop analysis. Mesh analysis is application of KVL and applicable for planner circuit only. Super position theorem:-superposition theorem states that, in any linear bidirectional circuit having more than one independent source, the response in any one of the branches equal to algebraic sum of responses caused by individual sources, while the rest of the sources are replaced by its internal resistance. Important point:- 1. Used for calculation of voltage and currents only. 2. Superposition theorem is only applicable for linear quantities. 3. It is not applicable for power calculations. because power is square of current or voltage. 4. Dependent source remains same in the analysis 5. Current source is opened and voltage source is shorted for suppressing the source. 6. Effect of one source is taken at a time by suppressing the sources 7. Super position theorem should be follow the principle of Addictivityand Homogenity. Thevenin s theorem:-any linear active complicated network which contain one or more than one voltage or current source across its load terminal can be replace by a single voltage source and a series impedance. Method of solving thevenin s theorem:- 1. First remove the element in which current and voltage is to be found. 2. From disconnected terminals, reduce the circuit to a single resistance after suppressing sources. 3. Reconsider all the sources as they were and find across the particular terminal. 4. We have or and series internal resistance. 5. Finally draw the equivalent diagram.

4 Norton s theorem:-any linear active complicated network which contain one or more than one voltage or current source across its load terminal can be replace by a single voltage current source and a parallel impedance. It is dual of thevenin stheorem After removing the element the terminals is shorted and the short circuit current is calculated. Maximum power transfer theorem: -this theorem is used to find the value of load resistance in which source will transfer maximum power. In the case of DC In the case of AC load impedance is equal to complex conjugate of source impedance Efficiency:- ) Millman s Theorem Millman s Theorem is a theorem which helps in simplifying electrical networks with a bunch of parallel

5 branches. It was invented by the Russian born, American Engineer Jacob Millman. Millman s Theorem can be used to find the potential difference between two points of a network which contains only parallel branches. * Contains Only Parallel branches. Following requirements can be applied with Millman s theorem: * Contains one and only one resistance and source in each branch. Sometimes even though a circuit does not full-fill both the requirements the circuit can be converted into an equivalent circuit which full-fills both of the above requirements and the process of conversion is done as following: Note: It is easier to apply Millman s theorem to a circuit if all the branches contains same type of source either voltage or current. The theorem can also be applied to a circuit containing both types of sources but often the process requires the use of ohm s law in each branch and is confusing and complex. Basic terms AC FUNDAMENTAL Cycle:-One complete set of positive and negative values of an alternating quantityis called a cycle. Periodic Time or Time period:- The time taken by the wave to complete a cycle is called periodic Time it is denoted by T Frequency :-The number of cycles per second is called frequency or periodicity. It is denoted by f Unit :- Instantaneous value :-The magnitude at a given time is called the instaneous value. Instantaneous Equation:-

6 Average Value :-It is the steady state current ( D.C. ) which transfer across any circuit thesame charge as it is transferred by that alternating quantity ( A.C.) the averagevalue I av over the complete cycle is zero. Therefore the average value is obtained for half cycle only or the average of the instant value in one half of the cycle is known as the average value. R.M.S. Value :- The RMS value of alternating current is given that steady d.c. currentwhich produces same heat as that produced by the alternating current passing?through on given resistance for the same period of time. For sinusoidal wave form only:- Current:- Voltage:- For Half wave rectified circuit wave form only:- Current:- Voltage:-

7 Maximum Value :This is also called crest value, peak value or amplitude. It is the highestvalue attained by the current or voltage in a half cycle. Form Factor :-Form factor of an A.C. is the ratio between R.M.S. value and mean value or Average value. Peak Factor: It is the ratio of maximum, value to R.M.S. Value Phase :-The angular displacement between two or more alternating quantitatesis known as phase or The meaning of phase is to indicate the relative positionbetween voltage and current components. The components may rise or fall atthe same time may lag the other or lead. Phase Difference: The difference between two sinusoidal quantities or the phases of these quantities at a given instant of time.

8 Pure resistive circuit:- Instantaneous Equation:-.(i) (2) By equation (1) and (2) Angle between voltage and current Vector diagram:- Power factor:- angle between voltage and current is zero Phasor diagram Power wave daigram:-

9 Instantaneous power Power consists of two part:- For complete cycle Hence power for whole cycle is Pure Inductive circuit:-

10 .(i) Integrating both side, we get Equation of current became (2) By comparing the equation (1) and (2) angle between voltage and current is

11 Current lags voltage by Power:- Instantaneous power For whole cycle:-

12 Pure capacitive circuit:-.(i) And..(2) By comparing the equation (1) and (2) angle between voltage and current is And current leads by voltage by Power factor=

13 Power: - Instantaneous power For whole cycle:- Power consumed in pure capacitive circuit is zero. Operator j

14 It should be also noted that Polar to Rectangular convertor:- Rectangular to polar

15 RL Series Circuit:- Voltage From Vector diagram It is clear that the applied voltage V leads by current I by angle From impedance triangle If the applied voltage and Then current

16 This consists of two part 1. A constant part which contribute real power. 2. A pulsating power Which has a frequency twice that of voltage and current? for whole cycle is zero. Hence average power Power Factor It may be define as (i) (ii) (iii) cosine of the angle of lead or lag the ratio the ratio

17 Active, Reactive and apparent power (i) Apparent power (S) It is given by the product of r.m.s. Values of applied voltage and circuit current. volt-amperes (VA) (ii) Active power ( P or W) It is the power which is actually dissipated in the circuit resistance. (iii) Reactive power (Q) It is the power developed in the inductive reactance of the circuit. These three powers are shown in the power triangle of fig from where it can be seen that Q- factor of a coil Reciprocal of powers factor is called the Q-factor of a coil its fingue of merit. It is also known as quality factor of the coil. If R is small as compared to reactance, then Q-factor = Z/R = L/R Series R-C circuit Now = or The denominator is called the impedance of the circuit. so,

18 In Impedance triangle it is found that I leads V by angle ϕ such that tan ϕ = Series R-L-C Circuit The term is known as the impedance of the circuit. Obviously (impedance) 2 = (resistance) 2 + (net reactance) 2 or Phase angle ϕ is given by tan ϕ = net reactance / resistance Power factor is cos ϕ = = Phase angle IS ϕ = AC Circuits Type of impedance Value of Impedance Phase angle for current power factor Resistance only R 0 1 Inductance only 90 lag 0 Capacity only 90 lead 0 Resistance and Inductance 0 < ϕ < 90 lag 1>p.f. > 0 lag Resistance and Capacitance 0 < ϕ < 90 lead 1>p.f. > 0 lead R-L-C between 0 < ϕ < 90 between 0 and Lag or lead unity lag or lead Series Resonance circuit:- We know that next reactance in an R-L-C circuit is

19 = Let such a circuit be connected across an a.c. source of constant voltage V but of frequency varying from zero to infinity. There would be a certain frequency of the applied voltage which would make X L equal to Xcin magnitude.in the case,x=0 an Z=R. Important Part:- When an R-L-C circuit is in resonance 1. Net reactance of the circuit is zero ( ) =0. Or X=0 2. Circuit impedance in minimum i.e. Z=R. Consequently, circuit admittance is maximum. 3. Circuit current is maximum and is given by 4. Power dissipated is maximum i.e. 5. Circuit power factor angle =0. Hence power factor cos ɵ=1. 6. although is greter than V C because of its resistance. 7. at resonance, 8. Q = tan = tan 0 = 0*. Q-Factor of a resonant series circuit It is given by the voltage magnification produced in the circuit at resonance

20 Where ϕ is power factor of the coil The Q-factor may also be defined as under:- In other words, Parallel Circuits:- Vector or pharos method = Consider the circuits shown. here, two reactors A and B have been joined in parallel Across anr.m.s supply of V volts. The voltage across two parallel branches is the same, but currents through them are different. For Branch A, Current lags behind the applied voltage by (Fig 14.2)

21 For Branch A, ( ) Current leads V by Sum of the active component of Sum of the reactive component of and = and ( ) Admittance Method Admittance of a circuit is defined as the reciprocal of impedance. Its symbol is Y.

22 Complex or pharos Algebra Now Total current ( ) Y = total admittance = Similarly, ( ) The polar form for admittance is Y=Y ɸ is as given above. (B/G) Total current I= VY; I 1 = VY 1 and I 2 = VY 2 If V = V and Y=y ɸ then I = VY = V y ϕ = VY ϕ In general, if V=V and Y=Y, then I =VY6 =V Y =VY + Parallel Resonance Circuit:-

23 Net reactive component = And impedance If coil is pure inductive Same as series circuit. Current:-

24 The selectivity or Q-factor for a parallel resonance circuit is generally defined as the ratio of the circulating branch currents to the supply current and is given as: Resonance curve:- 1. A 1 kω, 1 W resistor can safely pass a current of A. 30 ma. B. 60 ma. C. 40 ma. D. 100 ma. MCQs

25 2. Two resistors are connected in parallel across a battery of 2 V and an current flow through the combine resistors is 2 A. It one of the resistors is disconnected, the current will become 1.5 A, then what will be the resistance of that disconnected resistors? A. 2 Ω. B. 4 Ω. C. 1 Ω. D. 0.5 Ω. 3. Parallel combination of three 3 ohm resistors, connected in series with parallel combination of two 2 ohm resistors, what will be the equivalent resistance of overall combination? A. 2 Ω. B. 3 Ω. C. 5 Ω. D. 1 Ω. 4. When a numbers of different valued resistance are connected in series, the voltage drop across each of the resistor is A. proportional to resistance. B. proportional to current. C. proportional to square of current. D. equal. 5. All the resistances in figure shown below are 1 Ω each. The value of current in Ampere through the battery is A. 1 / 15. B. 2 / 15. C. 4 / 15. D. 8 / Two wires A and B of same material and length l and 2l have radius r and 2r respectively. The ratio of their specific resistance will be A. 1 : 4. B. 1 : 2. C. 1 : 1. D. 1 : If the length of a wire of resistance R is uniformly stretched n times its original value, its new resistance is A. nr. B. n 2 R. C. R / n. D. R / n The resistance between the opposite faces of 1 m cube is found to be 1 Ω. If its length is increased

26 to 2 m, with its volume remaining the same, then its resistance between the opposite faces along its length is A. 1 Ω. B. 2 Ω. C. 4 Ω. D. 8 Ω. 9. A wire of length l and of circular cross - section of radius r has a resistance of R ohms. Another wire of same material and of x-section radius 2r will have the same R if the length is A. 2l. B. l / 2. C. l2. D. 4l. 10. The insulation resistance of a cable of 10 km is 1 MΩ. For a length of 100 km of the same cable, the insulation resistance will be A. 1 MΩ. B. 0.1 MΩ. C. 10 MΩ. D MΩ. 11. The hot resistance of the filament of a bulb is higher than the cold resistance because the temperature coefficient of the filament is A. positive. B. negative. C. zero. D. infinite. 12. The temperature coefficient of resistance of an insulator is A. positiveand independent of temperature. B. negative and dependent on temperature. C. negativeand independent on temperature. D. positive and dependent on temperature. 13. Four resistances 80 Ω, 50 Ω, 25 Ω and R are connected in parallel. Current through 25 Ω resistance is 4 A. Total current of the supply is 10 A. The value of R will be A Ω. B Ω. C Ω. D Ω. 14. Three parallel resistive branches are connected across a DC supply. What will be the ratio of the branch current I 1 : I 2 : I 3 if the branch resistances are in the ratio R 1 : R 2 : R 3 = 2 : 4 : 6 A. 6 : 4 : 2. B. 6 : 3 : 2. C. 2 : 4 : 6. D. 3 : 2 : When a resistor R is connected to a current source, it consumes a power of 18 W. When the same R is connected to a voltage source having the same magnitude as the current source, the power absorbed by R is 4.5 W. The magnitude of the current source and the value of R are A. 18 A and 1 Ω. B. 1 A and 18 Ω. C. 3 A and 2 Ω. D. 6 A and 0.5 Ω. 16. When all the resistances in the circuit are of 1 Ω each, the equivalent resistance across the points A and B will b

27 A. 1 Ω. B. 0.5 Ω. C. 1.5 Ω. D. 2 Ω. 17. Resistivity of metals is expressed in terms of A. μω. B. μω - cm / C. C. μω - cm. D. μω. 18. Resistivity of copper is of the order of A μω - cm. B μω - cm. C μω - cm. D. 172 μω - cm. 19. Resistivity of copper at absolute zero is A μω - cm. B μω - cm. C. negligibly small. D μω - cm. 20. Two resistances R 1 and R 2 give combined resistances 4.5 Ω and 1 Ω when they are connected in series and parallel respectively. What would be the values of these resistances? A. 3 Ω and 6 Ω. B. 1.5 Ω and 3 Ω. C. 3 Ω and 9 Ω. D. 6 Ω and 9 Ω. 21. Which of the following may be value of resistivity of copper? A B C D Two equal resistors R connected in series across a voltage source V dissipate power P. What would be the power dissipated in the same resistors when they are connected in parallel across the same voltage source? A. 4P. B. P C. 2P. D. 16P. 23. Two identical resistors are first connected in parallel then in series. The ratio of resultant resistance of the first combination to the second will be A. 4. B

28 C. 2. D The ratio of the resistance of a 200 W, 230 V lamp to that of a 100 W, 115 V lamp will be A B. 2. C. 4. D The resistance of 200 W, 200 V lamp is A. 100 Ω. B. 200 Ω. C. 400 Ω. D. 800 Ω. 26. Two 1 kω, 1 W resistors are connected in series. Their combine resistance and wattage will be A. 2 kω, 0.5 W. B. 1 kω, 1 W. C. 0.5 kω, 2 W. D. 2 kω, 1 W. 27. Three 3 Ω resistors are connected to form a triangle. What is the resistance between any two of the corner? A. 9 Ω. B. 6 Ω. C. 3 Ω. D. 2 Ω. 28. A wire of 0.14 mm diameter and specific resistance 9.6 μω - cm is 440 cm long. The resistance of the wire will be A. 9.6 Ω. B Ω. C Ω. D Ω. 29. A 10 Ω resistor is stretched to increase its length double. Its resistance will now be A. 40 Ω. B. 20 Ω. C. 10 Ω. D. 5 Ω. 30. Specific resistance is measured in A. mho. B. ohm. C. ohm - cm. D. ohm/cm. 31. A wire of resistance R has it length and cross - section both doubled. Its resistance will become A. 0.5R. B. R. C. 2R. D. 4R. 32. A cube of material of side 1 cm has a resistance of Ω between its opposite faces. If the same volume of the material has a length of 4 cm and a uniform cross - section, the resistance of this length will be A Ω. B Ω. C Ω. D Ω. 33. Resistance of which material does not change with change in temperature?

29 A. Platinum. B. Metal alloys constantan and manganin. C. Brass. D. Tungsten. 34. The hot resistance of a tungsten lamp is about 10 times the cold resistance. Accordingly, cold resistance of a 100 W, 200 V lamp will be A. 400 Ω. B. 40 Ω. C. 4 Ω. D. 800 Ω. 35. For same voltage, the ratio resistance of 100 W lamp to resistance of 25 W lamp is A. 16. B. 4. C. 1/4. D Which of the following has least resistivity? A. Copper. B. Lead. c. C. Mercury. D. Aluminum. 37. Which of the following lamp has least resistance? A. 200 W, 220 V. B. 100 W, 220 V. C. 60 W, 220 V. D. 25 W, 220 V resistors of 200 Ω each are connected in parallel. Their equivalent resistance will be A. 1 Ω. B. 200 Ω. C. 400 Ω. D. 4 kω. 39. The resistance of 100 W, 200 V lamp is A. 200 Ω. B. 400 Ω. C. 800 Ω. D Ω. 40. A resistance having rating 10 ohms, 10 W is likely to be a A. metalic resistor. B. carbon resistor. C. wire wound resistor. D. variable resistor. 41. The rating of fuse wire is always expressed in A. ampere-hours. B. kwh. C. amperes. D. ampere-volts. 42. Three identical resistors are first connected in parallel and then in series. The resultant resistance of the first combination to the second will be A. 9 times. B. 1 / 9 times. C. 3 times.

30 D. 1 / 3 times. 43. Which of following materials has the least resistivity? A. Lead. B. Zinc. C. Copper. D. Mercury. 44. Which resistor will be physically larger in size? A. 100 Ω, 10 W. B. 10 Ω, 50 W. C. 1 MΩ, 1/2 W. D. 1 kω, 1 W. 45. When resistance element of a heater fuses and then we reconnect it after removing a portion of it, the power of heater will A. Decrease. B. increase. C. remain constant. D. none of these. 46. When current flows through heater coil it glows but supply wiring does not glow because A. supply wiring is covered with insulation layer. B. current through supply line flows at slower speed. C. resistance of heater coil is more than the supply wires. D. supply wires are made of superior materials. 47. Two resistor are said to be connected in parallel when A. same current passes in turn through both. B. both carry the same value of current. C. total current equals the sum of branch currents. D. voltage across each resistance are same but currents are different. 48. The maximum current rating for a 10 kω, 0.5 W resistor is A ma. B ma. C ma. D ma. 49. The electrical resistance of human body is around A. 5 ohms. B. 25 ohms. C. 250 ohms. D ohms. 50. You have to replace 1500 Ω resistor in radio. You have no 1500 Ω resistor but have several 1000 Ω ones which you would connect A. two in parallel. B. two in parallel and one in series. C. three in series. D. three in parallel. 51. Nodal analysis can be applied for A. planar networks. B. non planar networks. C. both planner and non planner networks. D. neither planner nor non planner networks. 52. Mesh analysis is applicable for A. planar networks

31 B. non planarnetworks C. both planner and non planner networks. D. neither planner nor non planner networks. 53. Super position theorem is not applicable for A. current calculations B. voltage calculations C. power calculations D. None of the above 54. KCL works on the principle of which of the following A. Law of conservation of charge B. Law of conservation of energy C. Both D. None of the above 55. KVL works on the principle of A. Law of conservation of charge B. Law of conservation of energy C. Both D. None of the above 56. In series RLC circuit, voltage across resistor, inductor and capacitor are 5V, 2V and 2V respectively. Find total voltage? A. 9V B. 4V C. 2V D. 5V 57. Voltage magnification will occur in which of the following case? A. Series resonance B. Parallel resonance C. Both D. None of the above 58. Current magnification will occur in which of the following case? A. Series resonance B. Parallel resonance C. Both D. None of the above 59. To obtain high efficiency, network is designed with which of the following? A. High Q factor B. Low Q factor C. Unity Q factor D. Zero Q factor 60. To obtain wide bandwidth, network is designed with which of the following? A. High Q factor B. Low Q factor C. Unity Q factor D. Zero Q factor 61. In series RLC circuit which of the following represents the Q factor? A. XC/R B. VR/V C. XL/R D. All of the above 62. In series RLC circuit what is the power factor just bellow the resonance frequency?

32 A. Lagging B. Leading C. Unity D. Zero 63. In series RLC circuit what is the power factor just above the resonance frequency? A. Lagging B. Leading C. Unity D. Zero 64. In RLC series circuit, at resonance condition the value of current is A. Maximum B. Minimum C. Zero D. None of the above 65. In parallel RLC circuit under resonance condition the value of current is A. Maximum B. Minimum C. Zero D. None of the above 66. By which of the following elements transients will not occur? A. R B. L C. C D. All of the above 67. For steady state current inductor acts as A. Short circuit B. Open circuit C. Voltage source D. Current source 68. In RL series circuit R=2Ω and L=10mH and applied voltage is 10V DC. Then find the current in the network? A. 0A B. 10A C. 5A D. 1A 69. In RC series circuit R = 2Ω, C = 2μF and 10V dc is applied. Then what is the value of current? A. 0A B. 2A C. 5A D. 10A 70. Time constant of RL series circuit is A. 2L/R B. RC C. L/R D. 2RC 71. Time constant of RC series circuit is A. L/R B. 2RC C. 2L/R D. RC

33 72. In RL series circuit R=2Ω and L=2mH. What is the value of time constant? A. 1msec B. 2msec C. 4msec D. 100sec 73. Time constant is the time taken for response to rise of maximum value? A. 100% B. 90% C. 63.2% D. 68.3% 74. Which of the following is the different one in terms of measurements? A. L/R B. RC C. 2L/R D. Q 75. In RLC parallel network R=2Ω, L=2mH and C=1μF. Find the value of time constant? A. 2μsec B. 2msec C. 4μsec D. 4msec 76. Resistor stores the energy in the form of A. Magnetic field B. Electrical field C. Both 1 and 2 D. None of the above 77. Transients are presents in the circuit when the circuit is having A. R B. L C. C D. Either 2 or In RLC series circuit R=2Ω, L=2mH and C=1μF and applied voltage is 10V dc. Then what is steady state current value? A. 5A B. 2A C. 1A D. 0A 79. Given network is having N nodes and b branches, then number of individual loops are A. N A. N-1 B. b-n+1 C. b-n In a series resonant circuit impedance is A. minimum. B. maximum. C. zero. D. none of these. 81. In the figure, the potential difference between points P and Q is

34 A. 6 V. B. -6 V. C. 10 V. D. 12 V. 82. In the circuit shown in figure if I 1 = 1.5 A, then I 2 will be A. 2 A. B. 1.5 A. C. 1 A. D. 0.5 A. 83. The value of current I flowing in the 1ohm resistor in the circuit shown in the given figure will be A. 5 A. B. 6 A. C. 0 A. D. 10 A. 84. An electrical circuit with 10 branches and 7 nodes will have A. 10 loop equations. B. 7 loop equations. C. 3 loop equations. D. 4 loop equations. 85. A 35 V source is connected to a series circuit of 600 Ω and R as shown. If a voltmeter of internal resistance 1.2 kω is connected across 600 Ω resistor, it reads 5 V. The value of R is

35 A. 2.4 k Ω. B. 1.2 k Ω. C. 3.6 k Ω. D. 7.2 k Ω. 86. In the circuit given, I = 1 A for Is = 0. What is the value of I for Is = 2 A? A. 4 A. B. 3 A. C. 2 A. D. 1 A. 87. For the circuit shown in the given figure the current I is given by A. 2 A. B. 1 A. C. 3 A. D. 4 A. 88. In the given figure the value of the source voltage is

36 A. 12 V. B. 30 V. C. 44 V. D. 24 V. 89. Consider the following circuit. What is the value of current I in the 5 ohm resistor in the circuit given in the figure? A. 0 A. B. 2 A. C. 3 A. D. 4 A. 90. In the given figure, the Thevenins equivalent voltage and impedance as seen from the terminals P - Q is given by A. 2 V and 5 Ω. B. 2 V and 7.5 Ω. C. 4 V and 5 Ω. D. 4 V and 7.5 Ω. 91. Consider the following circuit :

37 Switch is closed at t = 0Find i(0 +) A. 0. B. V/L C. V/R. D. V / {R + (sl + 1 / Cs)}. 92. In the circuit shown below if I = 2 A then find V? A. 5 V. B. 3 V. C. 2 V. D. 1 V. 93. What is I 1 in the given circuit? A. 0.5 A. B. 1 A. C. 1.5 A. D. 3 A. 94. Which of the following frequencies has the longest time period? A. 1 Hz B. 1 khz C. 10 Hz D. 10 khz 95. Maximum power will be delivered from an ac source to a resistive load in a network whenthe magnitude of the source impedance is equal to A. Half the load resistance B. Double the load resistance

38 C. The load resistance D. Zero 96. The delta equation of given star connected impedance Z QR is equal to o 40 ohm o (20 + j10)ohm o (5 + j10 / 3) ohm o (10 + j30) ohm 97. A star connected load has three equal impedance each of (40 + j30) Ω If the line current is 5 A then value of line voltage is A. 250 V. B V. C. 250 / 3 V. D. 200 V. 98. For a 3 - phase load balanced condition, each phase has the same value of. A. impedance. B. resistance. C. power factor. D. all of these. 99. Which of the following waves has unity form factor? A. Traingular wave B. Square wave C. Sine wave D. None of the above A circuit with resistor, inductor, and capacitor in series is resonant of 50 Hz. If all the values are now doubled, the new resonant frequency is A. f 0 / 2. B. f 0 / 4. C. 2f 0. D. still f In the circuit given below, the value of R required for the transfer of maximum power to the load having a resistance of 3Ω will be?

39 A. 3 Ω B. 10Ω C. 6Ω D. 9Ω 102. What is the total resistance of the given circuit? A. 92 ohm. B. 288 ohm. C ohm. D. 128 ohm Two capacitor C 1 and C 2 have C 1 =20μF and C 2 = 30μF, are connected in parallel across a 100V source. The net capacitance of the circuit is? A. 50 μf B. 10 μf C. 12 μf D. 60μμ 104. A 33 half-watt resistor and a 330 half-watt resistor are connected across a 12 V source. Which one(s) will overheat? A. 33 B. 330 C. both resistors D. neither resistor 105. When the pointer of an analog ohmmeter reads close to zero, the resistor being measured is A. Overheated B. Shorted C. Open D. reversed 106. In W, there are A. 25 kw B mw C. 2,500 µw D. 25 mw 107. A certain appliance uses 350 W. If it is allowed to run continuously for 24 days, how many kilowatthours of energy does it consume? A kwh B kwh C kwh D. 8.4 kwh

40 108. A power supply produces a 0.6 W output with an input of 0.7 W. Its percentage of efficiency is A. 8.57% B % C. 4.28% D. 85.7% 109. Find the Thevenin equivalent (VTH and RTH) between terminals A and B of the circuit given below. A V, 120 B V, 120 C V, 70 D V, Find the total current through R3 in the given circuit. A. 7.3 ma B. 5.5 ma C ma D. 1.8 ma 111. A 1.5 k resistor and a coil with a 2.2 k inductive reactance are in series across an 18 V ac source. The power factor is A. 564 B C D The voltages in Problem 5 are measured at a certain frequency. To make the resistor voltage less than the inductor voltage, the frequency is A. Increased

41 B. Decreased C. Doubled D. not a factor 113. In a series RL circuit, 12 V rms is measured across the resistor, and 14 V rms is measured across the inductor. The peak value of the source voltage is A V B V C. 2 V D. 20 V 114. To increase the current in a series RL circuit, the frequency A. should be increased B. should be decreased C. should be constant D. cannot be determined without values 115. Form factor is equal to peak factor in case of A. Square wave B. Triangle wave C. Saw tooth wave D. All of the above 116. If a pure inductor is connected across the ac source, the average power taken by the inductor is A. A few watt B. 100 watt C. 0 watt D. Maximum power 117. Average power taken by the pure capacitor is A. Zero B. Minimum C. Maximum D. Any of the above 118. In RLC series circuit R = 2Ω, L = 2mH and C = 1μF. Find the time constant of the circuit? A. 1 μsec B. 2 msec C. 2 μsec D. 4 msec 119. Which of the following is not a vector quantity? A. Linear momentum. B. Angular momentum. C. Electric field. D. Electric potential If conductance increases as temperature increases it is called as... A. Negative co-efficient B. Positive co-efficient C. Both 1 & 2 D. None of the above 121. What is mean by flow of electrons? A. Insulator B. Electric current C. Semiconductor D. Voltage 122. Which material has extremely large resistance?

42 A. Semiconductor B. Conductor C. Insulator D. None of the above 123. What is mean by the rate of flow of an electric charge? A. Electric current B. Electric potential C. Electric resistance D. None of the above 124. What is the unit of potential difference? A. Ohm B. Volt C. Watt D. Ampere 125. A 140 resistor is in parallel with an inductor having 60 inductive reactance. Both components are across a 12 V ac source. The magnitude of the total impedance is A B C. 90 D In a highly capacitive circuit A. actual power is more than its reactive power B. reactive power is more than actual power C. reactive power is more than apparent power D. apparent power is equal to the actual power 127. For the network shown in finger. The value of current in 8ohm resistors.(ssc-je : 2014) A. 4.8 A B. 2.4 A C. 1.5 A D. 1.2 A 128. Which of the following can not be connected in series unless they are identical? A. Voltage source. B. Current source. C. Both of above. D. Resistance In the given circuit, Thevenin voltage across the terminal AB is

43 A. -15 V B. 15 V C. 5 V D. 0 V 130. In the circuit, the maximum power that can be transferred to Load ZL is A. 250 W B. 500 W C W D W 131. Two sinusoidal currents are given by following equations : i 1 = 10sin( t+л/3) i 2 = 15sin( t-л/4) The phase difference between them is A. 105 B. 75 C. 15 D In a series RLC circuit that is operating above the resonant frequency, the current A. lags the applied voltage B. is in phase with the applied voltage C. leads the applied voltage D. is zero 133. If the resistance in parallel with a parallel resonant circuit is reduced, the bandwidth A. decreases B. disappears C. increases D. becomes sharper 134. At any resonant frequency, what voltage is measured across the two series reactive components? A. Reactive B. inductive and capacitive C. applied D. zero 135. The equation of an emf is given by e = I m [ (R 2 + 4ω 2 L 2 )]sin2ωt. The amplitude of the wave will be A. I m [(R 2 + 4ω 2 L 2 ) 1/2 ].

44 B. 2I m [R 2 + 4ω 2 L 2 ) 1/2 ]. C. [I m (R 2 + 4ω 2 L 2 )] 1/2. D. 2I m [(R 2 + 4ω 2 L 2 ) 1/2 ] The RMS value of sinusoidal voltage wave v = 200sinωt, is A V. B. 200 V. C. 100 V. D V In the given circuit, inductances L1 and L2, if L1 = 2L2 and Leqis 0.7 H, are A. 0.4 H and 0.8 H respectively B. 0.6 H and 0.3 H respectively C. 0.8 H and 0.4 H respectively D. 1.0 H and 0.5 H respectively 138. The Norton current at terminals A and B of the circuit shown at Figure. A. 1 B. -2 C. 2 D The Thevenin voltage across terminals 1and 2 of the circuit in Figure. A. 20V

45 B. 30V C. 40V D. 50V 140. A parallel resonant circuit can be employed A. as a high impedance. B. to amplify voltage. C. to reject a small band of frequencies. D. both A and C 141. When a sinusoidal voltage is applied across R-L series circuit havingr = XL, the phase angle will be A. 90. B. 45 lead. C. 45 lag. D. 90 leading A 20 mh inductor carries a sinusoidal current of 1 A rms at a frequency of 50 Hz. The average power dissipated by the inductor is A. 0 W. B W. C. 0.5 W. D. W A two terminal black box contains a series combination of a resistor and unknown two terminal linear device. As soon as the battery is connected to the black box the current is found to be zero. The device is A. an inductor. B. a resistor. C. a diode. D. an unknown The value of in the given circuit is:- A. 6.6Ω B. 3.6Ω C. 8.4Ω D. 9.6Ω 145. A wire of resistance R has it length and cross - section both doubled. Its resistance will become A. 0.5R. B. R. C. 2R. D. 4R.

46 146. A cube of material of side 1 cm has a resistance of Ω between its opposite faces. If the same volume of the material has a length of 4 cm and a uniform cross - section, the resistance of this length will be A Ω. B Ω. C Ω. D Ω 147. The equation for 25 cycles current sine wave having rms value of 30 amps, will be A. 42.4sin50πt. B. 30sin50πt. C. 30sin25πt. D. 42.4sin25πt If emf in a given circuit is given by e = 100sin628t, then maximum value of voltage and frequency will be A. 100 V, 100 Hz. B. 100 V, 50 Hz. C V, 100 Hz. D V, 100 H 149. The rms value of the voltage U(t)= 3 + 4cos(3t) A. 5 V. B V. C. 7 V. D. {3 + 2(1.141)} V 150. The form factor of sinusoidal alternating current is A. 0. B. 1. C D It is said that the two sinusoidal quantities are in phase quadrature when their phase difference is A. 30 B. 0 C. 90 D Consider a current sine wave whose rms value is 30 amperes. The equation for 25 cycles current sine wave will be A sin 50 π t B sin 25 π t C. 30 sin 50 π t D. 30 sin 50 π t 153. If E 1 = A sin ωt and E 2 = A sin (ωt Φ), then A. E1 leads E2 by Φ B. E1 lags E2 by Φ/2 C. E2 leads E1 by Φ D. E2 lags E1 by Φ 154. is the rms value of rectangular voltage wave with and amplitude of 10 V. A V B. 5.2 V C. 7.7 V D. 10 V 155. Consider 220 V, 50 Hz A.C. waveform. The form factor will be

47 A. 1.5 B C D Voltage V = 90 cos (ωt ). This may be represented as sine function by A. 90 sin (ωt 18.5 ) B. 90 sin (ωt ) C. 90 sin (ωt ) D. 90 sin (ωt 71.5 ) 157. The rms value of current i = cos (628t + 30 ) is A A B. 10 A C. 8 A D. 15 A 158. The negative maximum of a cosine waveform occurs at A. 0 B. 270 C. 180 D Let us say that the current and voltage both are out of phase by 90. The power will be A. Maximum B. Minimum C. Zero D. 1.1 VI 160. Which one of the following has the least value of form factor? A. Sine wave B. Square wave C. Rectangular wave D. Triangular wave 161. The frequency that has the longest period is A. 10 KHz B. 1 KHz C. 10 Hz D. 1 Hz 162. The waveform that has the least rms value for the same peak value of voltage is A. Triangular wave B. Sine wave C. Square wave D. Full wave rectified sine wave 163. Which of the following statement is false? A. The 480 vector will end up in second quadrant B. Every non-sinusoidal waveform has large number of harmonics C. A square wave has only even harmonics D. All of the above statements are true 164. The peak factor of a wave is A. Rms value / average value B. Average value / rms value C. Maximum value / rms value D. Maximum value / average value 165. If the load is same and the power factor of load is reduced, it will

48 A. Draw less current B. Draw more current C. Draw less current but power will be less D. Nothing will happen 166. The power factor of a load with Z = 36 Ω < -30 will be A leading B lagging C. 30 leading D. None of the above 167. A certain square wave has a period of 4 ms. Its fundamental frequency will be A. 0 Hz B. 230 Hz C. 250 Hz D. 430 Hz 168. The difference in period of two frequencies of 1MHz and 2 MHz is A. 0.5 milli-seconds B. 0.5 micro-seconds C. 1 milli-seconds D. 1 micro-seconds 169. A choke coil is used for controlling current in an A. Integrated circuit B. DC circuit only C. AC circuit only D. Both ac and dc circuits 170. will draw least current A. 40 W lamp B. 40 W induction motor C. 40 W tube light D. None of the above 171. Which of the following statements is not valid for ac currents? A. Alternating current develops eddy current losses B. Alternating current interferes with communication lines C. Alternating current provides better safety as compared to direct current D. Alternating current is suitable for batteries 172. For the magnetizing component of a transformer, power factor is A. Unity B. Zero C. 0.8 leading D. 0.8 lagging 173. When current flows through the transmission lines, the two significant effects are A. Thermal and magnetic effects only B. Luminous and chemical effects only C. Chemical and magnetic effects only D. Luminous and magnetic effects only 174. To improve power factor of an inductive circuit, a capacitor is connected to it in A. Depends on the value of the capacitor B. Either series or parallel C. Parallel D. Series 175. The capacitors for power factor correction are rated in terms of

49 A. VA B. KVAR C. Voltage D. KW 176. For an audio signal of time period sec, the frequency is Hz A Hz B. 10 Hz C. 1 Hz D. 50 Hz 177. Ohm s law (E = IR) A. Can be applied to a.c similar to that of d.c. B. Can be applied to a.c. but after replacing R by Z (impedance) C. Can never be applied to a.c D. None of the above 178. Determine V x in the given circuit A. 6V B. 8V C. 12V D. 16V 179. For symmetrical wave form average value of one full cycle is A. 1 B C D Form factor is equal to peak factor in case of A. Square wave B. Triangle wave C. Saw tooth wave D. All of the above 181. If a pure inductor is connected across the ac source, the average power taken by the inductor is A. A few watt B. 100 watt C. 0 watt D. Maximum power 182. In RLC series circuit R = 2Ω, L = 2mH and C = 1μF. Find the time constant of the circuit? A. 1 μsec

50 B. 2 msec C. 2 μsec D. 4 msec 183. What is form factor? A. Average value / R.M.S. value. B. Average value / Peak value. C. Instantaneous value / Average value. D. R.M.S. value / Average value Two equal resistors R connected in series across a voltage source V dissipate power P. What would be the power dissipated in the same resistors when they are connected in parallel across the same voltage source? A. 4P. B. P. C. 2P. D. 16P Specific resistance is measured in A. mho. B. ohm. C. ohm - cm. D. ohm/cm Which of the following lamp has least resistance? A. 200 W, 220 V. B. 100 W, 220 V. C. 60 W, 220 V. D. 25 W, 220 V Which of the following carbon coded resistor has value of 10 kohm with 20% tolerance? A. Brown, black, orange and no tolerance band. B. Yellow, violet, yellow and silver stripes. C. Orange, orange, black and gold stripes. D. Red, red, green and silver stripes If emf in a given circuit is given by e = 100sin628t, then maximum value of voltage and frequency will be A. 100 V, 100 Hz. B. 100 V, 50 Hz. C V, 100 Hz. D V, 100 Hz What would be the power given by source V2? B. -5 W. C. 10 W. D. 0 W. A. 5 W.

51 190. Three equal resistors each equal to R ohm are connected as shown in fig. The equivalent resistance between points A and B is: A. R B. 3R C. R/3 D. 2R/ The current Io of Figure 1 is: A. 4 A B. -2 A C. 4 A D. 16 A 192. For the circuit given in the fig, the thevenis s voltage and resistance as seen at AB are represented by: A. 5 V, 10 Ω B. 10V, 10 Ω C. 5 V, 5 Ω D. 54V, 15 Ω 193. Calculate the value of load resistance RL to which maximum power may be transferred from the source shown in figure

52 A. A ohm B. 60 ohm C ohm D. 100 ohm 194. If the p and T circuits in figure below are equivalent, then R1, R2, R3 respectively are A. 9 W, 6 W, 6 W B. 6 W, 6 W, 9 W C. 9 W, 6 W, 9 W D. 6 W, 9 W, 6 W 195. Find the value of I in the circuit. A. 2 amp B. 3 amp C. 4 amp D. 1 amp 196. Find RAB for the circuit shown in the figure.

53 A. 10Ω B. 20Ω C. 8Ω D. 12Ω 197. In the circuit below, the current through E2 is A. 9 A discharging B. 9 A charging C. 1 A discharging D. 1 A charging 198. Norton equivalent of the circuit given below is 199. Which of the following carbon coded resistor has value of 10kohm with 20% tolerance?

54 A. Red, red, green and silver stripes B. Yellow, violet, yellow and silver stripes C. Orange, orange, black and gold stripes D. Brown, black, orange and no tolerance band Conductance is expressed in terms of A. ohm / m B. m / ohm C. mho / m D. mho Which of the following could be the value of resistivity of copper? A. 1.7 x 10-8 ohm-cm B. 1.7 x 10-6 ohm-cm C. 1.6 x 10-5 ohm-cm D. 1.7 x 10-4 ohm-cm 202. Current I in the figure is A. 1.5A B. 0.5A C. 3.5A D. 6A 203. Twelve wires of same length and same cross-section are connected in the form of a cube as shown in figure below. If the resistance of each wire is R, then the effective resistance between P and Q will be o R o 5 / 6 R o 3 / 4 R o 4 / 3 R. Questions 88 to 91 refer to Figure given below Three lamps are in circuit as shown in Figure given above. The lamp of 100 W will have maximum brightness when A. key k1 is closed, k2 is open and k3 is closed B. k1 is open, k2 is closed and k3 is open

55 C. k1 is open, k2 is closed and k3 is also closed D. k1 is closed, k2 is open and k3 is also open When switches k1 and k2 are open and k3 is closed A. 100 W lamp will glow brighter than 40 W lamp B. 40 W lamp will glow brighter than 100 W lamp C. Both will glow at their full brightness D. Both will glow at less than their full brightness Which of the following statements is necessarily correct? A. 40 W bulbs will always glow at full brightness B. 100 W bulb will always glows at full brightness C. Whatever be the position of keys, at least one 40 W bulb will always glow D. Whenever current flows through the circuit, 100 W bulb will always glow Three resistance of 6 ohm each are connected as shown in Figure given below. The equivalent resistance between X 1 and X 2 is A. 2 ohm B. 4 ohm C. 8 ohm D. 12 ohm For the circuit shown in the figure given below, the meter will read A. 1 A B. 5 A C. 10 A D. 25 A Resistance between X 1 and X 2 is A. 10 ohm B. greater than 10 ohm C. 0 D. less than 10 ohm The four stripes of a resistor are yellow-violet-orange-gold. The value of resistor should be

56 A. 470 ohms ± 5 % B. 47 kilo ohm ± 5% C. 47 mega ohms ± 5% D ohms ± 10% In the figure below find the value of Resistance R in Ohms: A. 10 B. 20 C. 30 D The value of resistance R in the figure below is: A. 2.5 Ohms B. 5 Ohms C. 7.5 Ohms D. 10 Ohms 213. Kirchhoff s Current Law is applicable to only: A. Close looped Networks. B. Electronics Circuits. C. Electrical Circuits. D. Junctions in a network According to KVL the algebraic sum of all the IR drops and Emfs in any closed loop of a network: A. Dependent on the total voltage supplied. B. Varies according to the type on circuit. C. is always positive, D. is equal to zero.

57 215. A 35 V source is connected to a series circuit of 600 ohms an R as shown. If a voltmeter of internal resistance 1.2 Kilo ohms is connected across 600 ohm resistor it reads 5 V. The value of R is. A. 1.2 Kilo Ohms B. 2.4 Kilo Ohms C. 3.6 Kilo Ohms D. 7.2 Kilo Ohms 216. If all the resistances in the circuit are one ohm. Find the equivalent resistance between points A and B. A. 1 Ohm B. 0.5 Ohm C. 2 Ohms D. 1.5 Ohms 217. In the following circuit the total current through the voltage source V 0, I is equal to:

58 A. One Ampere B. Two Ampere C. Three Ampere D. Four Ampere 218. Two heaters; both rated 1000 Watt, 250 volt; are connected in series to a 250 voltage, 50 Hz power supply. The total power drawn from the source would be: A Watts B. 500 Watts C. 250 Watts D Watts 219. Two light bulbs rates 40 watt and 60 watt are connected in series to the mains power supply. Then. A. Both light will not glow. B. Both light will glow equally. C. 60 watt light will glow brighter. D. 40 watt light will glow brighter How many 200W/220 V incandescent lamps connected in series would consume the same amount of power as 100W/ 220V incandescent lamp? A. Not Possible. B. 4 C. 3 D A network has 4 nodes and 3 independent loops what is the number of branches in the network? A. 5 B. 6

59 C. 7 D A network with 10 branches and 7 nodes will have A. 3 loop equations. B. 4 loop equations. C. 7 loop equations. D. 10 loop equations In an electrical network to neglect a current source the current source is: A. Open Circuited. B. Short Circuited. C. Replaced by a capacitor. D. Replaced by an Inductor A network have 10 nodes and 17 branches. The number of different node pair voltage would be: A. 7 B. 9 C. 45 D If the number of branches in a network is B, the number of nodes is N. and the numbers of dependent loops is L. Then the numbers of independent node equations will be: A. N+L-1 B. B-1 C. B-N D. N A constant current source supplies 300 ma to a load of 1 kilo ohms. When the load is changed to 2 kilo ohms the current through the load will be: A. 150 ma B. 300 ma C. 600 ma D. 30 ma 227. To neglect a voltage source, The terminals across source are: A. open circuited. B. short circuited. C. replaced by some resistance. D. replaced by an inductor Kirchhoff s laws are valid for A. linear circuits only.

60 B. passive time invariant circuits. C. nonlinear circuits only. D. both linear and non linear circuits, 229. Kirchhoff s voltage laws are valid for A. IR drop. B. battery EMF. C. junction voltage, D. both "a" and "b" In the following circuit; what is the total power delivered by the 24v power supply? A. 96 W B. 114 W C. 192 W D. 288 W 231. The current through the 3 Ohms resistor in the circuit below is: A. 0 ma B. 1 ma C. 2 ma D. 6 ma 232. Assuming ideal elements in the circuit shown below. The voltage across A, B : VAB is?

61 A. -3 V B. 0 V C. 3 V D. 5 V 233. In the interconnection of ideal sources shown in the figure below, It is known that the 60 V source is absorbing power. What is the value of I in the current source I 0? A. 10 A B. 13 A C. 15 A D. 18 A 234. The current through 120 Ohms resistor on the circuit shown in the figure is: A. 1 A B. 2 A C. 3 A D. 4 A

62 235. For the network shown in the figure, what is the voltage across the current source I? A. V - RI B. V + RI C. Zero D. RI - V 236. In the circuit shown in the figure, The value of the current through 3 ohms resister will be: A A B A C A D. 2.5 A 237. When a resistor R is connected to a current source, it consumes a power of 18 watts. When the same R is connected to a voltage source having same magnitude as the current source, the power absorbed by R is 4.5 Watts. The magnitude of the current source and the value of R are: A. 18 Amps and 1 Ohms. B. 3 Amps and 2 Ohms. C. 1 Amps and 18 Ohms. D. 6 Amps and 0.5 Ohms For the circuit below, the value of RV is adjusted such that the current through RL is zero. What is the value of RV?

63 A. 1 Ohms B. 2 Ohms C. 3 Ohms D. 4 Ohms 239. In the circuit below the value of all the resistances is R Ohms. The switch is initially open. What happens to the Lamp s intensity when the switch is closed? A. Increase. B. Decrease C. Remains the same. D. Depends upon the value or R Superposition theorem is not applicable for: A. Voltage calculations. B. Bilateral elements. C. Power calculations. D. Passive elements.

64 241. Which of the following theorem is applicable for both linear and nonlinear circuits? A. Superposition theorem. B. Thevenin's theorem. C. Norton's theorem. D. none of these In the circuit shown in figure, what will be the value of current i through the voltage source when v=4 Volts. A. one amps B. two amps C. zero amps D. three amps 243. In the circuit shown, what is the value of the current i? A. one amps B. two amps C. three amps D. four amps 244. In the network shown below, what is the current i, in the direction shown?

65 A. 0 amps B. 1/3 amps C. 5/6 amps D. 3 amps 245. In the circuit given below, what is the voltage across the current source Is? A. 0 V B. 2 V C. 3 V D. 6 V 246. In the circuit shown below, what is the voltage across 5 Ohms resistor? A. -30 V B. 30 V C V D V 247. For the circuit given in the figure below, the power delivered by the 2 V source is :