## practice set

### SSC JE ELECTRICAL PRACTICE SET - 3

1.
 The energy stored in a capacitor as a function of voltage (V) is given by A CV2 B $\frac{1}{2}$ CV2< C $\frac{1}{2}\fra D None of these Answer : B Explanation : Energy stored in a capacitor  = $\frac{1}{2}$  QV $=&space;\frac{1}{2}$  CV.V   [ $\therefore$ Q = CV]   = $\frac{1}{2}$ CV2                              Where, Q = change stored in capacitor plate                                               V = developed voltage across capacitor plate                                               C = capacitor of the capacitor
2.
 A 100Ω, 1 watt resistor can sustain a maximum current of A 100 mA B 10A C 1A D None of these Answer : A Explanation : P = I2R  $I=&space;\sqrt{\frac{P}{R}}=&space;\sqrt{\frac{1}{100}}=&space;\frac{1}{10}=&space;\frac{1}{10}\times&space;\frac{10^{-3}}{10^{-3}}A=&space;\frac{1000}{10}mA=&space;100mA$
3.
 If all the three resistances of a given Delta network are 15Ω each, then all the three resistances of the equivalent star will be A 45 Ω each B 30 Ω each C 5 Ω each D 15 Ω each Answer : C Explanation : Equivalent star resistance of each phase  = $\frac{15\times&space;15}{15+15+15}=&space;\frac{15\times&space;15}{3\times&space;15}=&space;5\Omega$
4.
 If all the three resistances of a given star network are 10 each, then all the three resistances of the equivalent delta network A Will be 30 Ω each B Will be 3.33 Ω each C Will not be all equal D  Will be 20 Ω each Answer : A Explanation : Equivalent delta resistance of each phase   =  $\frac{R_{1}R_{2}+R_{2}R_{3}+R_{3}+R_{1}}{R_{3}}$                            Where, R1 , R2 and R3 all are three star resistances and R1 = R2 = R3 = 10 Ω                            $\therefore$  Equivalent delta resistance  =  $\frac{10&space;×10+10×10+10&space;×10}{10}=&space;\frac{300}{10}$  =  30 Ω
5.
 An electrical network with seven independent branches and five independent nodes excluding the reference node should preferably be solved by A Mesh current analysis B Node voltage analysis C Kirchoff’s  current law D None of these Answer : A Explanation : For mesh current analysis, no. of independent  mesh  or loop equations m are                                m  = b – n + 1                               Where, b = no. of branches                                               n   = no. of nodes                              $\therefore$  m = 7 -5 + 1  =  3
6.
 Most commonly employed trivalent impurities are A Boron, indium B Arsenic, antimony C Boron, arsenic D Indium, antimony Answer : A Explanation : Trivalent impurity (such as Boron, indium) has three valance electrons in their outermost shell, it is also known as p-type impurities in the case of transistor action.
7.
 Most commonly employed pentavalent  impurities are A Boron, indium B Aluminium , antimony C Arsenic , indium D Arsenic , antimony Answer : D Explanation : pentavalent impurity (such as Arsenic, Antimony) has five valance electrons in their outermost shell, it releases electrons into the material in which it is added so it is also known as n-type impurities in the transistor action
8.
 An N-type semiconductor as a whole is A Electrically neutral B Positively charged C Negatively charged D None of these Answer : A Explanation : An n-type semiconductor as a whole is ordinary metal like copper so it is basically electrically neutral as a whole material in which conduction takes place by application of potential difference
9.
 Which of the following is the dimensional formula for conductivity A M- 1 L- 3 T3 A2 . B ML3 T-3 A-2 . C M2 L2 T-3 A-2 . D ML2 T3 A-2 . Answer : A Explanation :
10.
 Which of the following is the  CORRECT  expression for the capacitance of a parallel plate capacitor A $\frac{\varepsilon&space;A}{d}$ B $\frac{\varepsilon&space;A^{2}}{d}$ C $\varepsilon&space;A^{2}d^{2}$ D $\frac{A^{2}d}{\varepsilon&space;}$ Answer : A Explanation :
11.
 In a series combination of several inductors, the equivalent inductance is  ________ . A Equal to the largest inductance of the combination. B Lower than the largest inductance of the combination. C Lower than the smallest inductance of the combination. D Greater than the largest inductance of the combination. Answer : D Explanation :
12.
 Which of the following is the reciprocal of resistivity A Reluctivity B Susceptibility C Conductivity D Permittivity Answer : C Explanation :
13.
 Determine the value of equivalent inductance, if 4 inductors having inductance  L  are connected in parallel A 4L B L/4 C 4/L D 8L Answer : B Explanation :
14.
 Determine the conductance (in Siemens) of a conductor, when the potential difference between the ends of the conductor is  30 V and the current flowing through the conductor is 3A A 0.1 B 1.1 C 2.4 D 4.2 Answer : A Explanation :
15.
 How much power (in W) will be dissipated by a 10 ohms resistor, when the current through the resistor is  3 A A 30 B 40 C 60 D 90 Answer : D Explanation :
16.
 Determine the value of resistance (in ohms)  of a resistor at 40 degree Celsius, when the resistance has a resistance of  10 Ohms  at  0 degree Celsius and the temperature coefficient at  0 degree Celsius is  0.04 A 20 B 23 C 24 D 26 Answer : D Explanation :
17.
 Determine the energy stored (in J)  by a  5 H inductor, when the current flowing through the inductor is  6 A> A 94 B 90 C 60 D 40 Answer : B Explanation :
18.
 Determine the equivalent resistance (in Ohms) for the circuit given below  Figure A 2 B 4 C 6 D 9 Answer : B Explanation :
19.
 Determine the resistance (in Ohms) of resistor when the potential difference between the ends of the resistor is 24 V  and the current flowing through the resistor is 3 A A 12 B 10 C 8 D 4 Answer : C Explanation :
20.
 Determine the value of current I3 (in A)  for the diagram given below Figure A 1 B 2 C 3 D 4 Answer : A Explanation :
21.
 Which of the following statement is TRUE A The current always flows in the direction of flow of electrons. B The current always flows opposite to the direction of flow of electrons. C The current always flows from negative terminal to positive terminal. D The electrons always flows from positive terminal to negative terminal. Answer : B Explanation :
22.
 Determine the  Norton’s resistance  (in Ohms) between terminal  A and B for the circuit given below Figure A 6.5 B 5.4 C 4.5 D 3.5 Answer : D Explanation :
23.
 Determine the value of current  I (in A)  drawn from the voltage source for the circuit given below Figure A 2.5 B 3.4 C 4.3 D 6.5 Answer : C Explanation :
24.
 Determine the value of source resistance (in Ohms) for transmitting maximum power from the source to the load, when the load impedance of the circuit is  10 – j2 Ohms A 2 B 10 C -2 D -10 Answer : B Explanation :
25.
 Determine the power (in W) delivered from the source for the circuit given below Figure A 23.8 B 26.6 C 24.6 D 22.6 Answer : A Explanation :
26.
 Determine the value of Thevenin’s equivalent resistance (in Ohms) across terminal  A and B  for the electrical circuit given below Figure A 1 B 2 C 6 D 8 Answer : B Explanation :
27.
 Determine the value of load resistance (in ohms) for a circuit, when the maximum power transferred from the source of  50 V  to the load is  25 W A 50 B 40 C 35 D 25 Answer : D Explanation :
28.
 What will happen to the inductance, if number of turns of the coil is decreased A Increase B Decreases C Remain same D None of these Answer : B Explanation :
29.
 If the area of cross-section is reduced to half of its original value, then what will happen to the flux density A Doubled B Halved C Remain same D One-fourth Answer : A Explanation :
30.
 Calculate the value of flux leakage coefficient, if  𝛷g is the air gap flux and 𝛷a is the flux in iron core A 𝛷g / 𝛷a B 𝛷a / 𝛷g C 𝛷a × 𝛷g D 𝛷a + 𝛷g Answer : A Explanation :
31.
 The graph shown represents the  B-H curve for  ________ Figure A Glass B Steel C Iron D Air Answer : D Explanation :
32.
 A conductor of length  0.6 m is situated at the right angle to a  uniform magnetic field of flux density  4 Wb/sq. m. The conductor is moving with a velocity of 50 m/s. calculate the emf induced (in V) n the conductor A 100 B 115 C 118 D 120 Answer : D Explanation :
33.
 A  600-turn coil has a resistance of  7 ohms and an inductance of  0.8 H. if one-fifith of the turns are removed, then determine the new inductance  (in H). A 0.512 B 0.25 C 2 D 2.5 Answer : A Explanation :
34.
 A magnetic circuit of reluctance  3000 A-turns/Wb is wounded by a wire of  400 turns. Determine the average emf induced (in V)  in the coil, if a current of  2 A  is flowing in the coil is reversed in  15 s A 14.24 B 16.28 C 17.96 D 19.62 Answer : A Explanation :
35.
 For the figure shown below, the permeability in the core is  4 × 10- 4 Wb/A-turns-m. what is the value of flux density (in T) in the core Figure A 0.2 B 0.382 C 0.6 D 1 Answer : B Explanation :
36.
 Which of the following represents the quality factor of a series  RLC  circuit A $\frac{1}{R}\sqrt{\frac{L}{C}}$ B $\frac{1}{R}\sqrt{\frac{C}{L}}$ C $R^{2}\frac{L}{C}$ D $R^{2}\frac{C}{L}$ Answer : A Explanation :
37.
 Which of the following represents the relation between the peak value and  RMS  value of voltage for a sine wave A $V_{rms}=&space;1.414&space;V_{peak}$ B $V_{rms}=&space;0.637&space;V_{peak}$ C $V_{rms}=&space;0.424&space;V_{peak}$ D $V_{rms}=&space;0.707&space;V_{peak}$ Answer : D Explanation :
38.
 Determine the average value of an alternating current (in A)  when the peak value of the current is  10 A A 14.14 B 10.63 C 6.37 D 4.36 Answer : C Explanation :
39.
 What will be the frequency (in Hz) of a sinusoidal waveform, when the time period of the wave is  25 ms A 40 B 50 C 60 D 80 Answer : A Explanation :
40.
 Determine the total impedance (in ohms)  of a series  RLC  circuit having a resistance of  10 Ohms, capacitive reactance of  2 ohms  and inductive reactance of  6 ohms,  connected in a series across a  200 V,  50 Hz supply A 8.64 B 10.77 C 12.21 D 14.65 Answer : B Explanation :
41.
 Determine the value of phase current (in A) for a balanced delta connected system, when the value of line current is  8.7 A. A 8 B 7 C 6 D 5 Answer : D Explanation :
42.
 What will be the value of inductance (in mH)  connected in parallel with a capacitance of 4 F in a series  RLC  circuit having a quality factor 2, when the resonant frequency is  6 rad/sec A 2 B 3 C 5 D 7 Answer : B Explanation :
43.
 What will be the value of average power  (in W), if a sinusoidal voltage applied across a series  RC circuit is  20 sin V and the current flowing in the circuit is  10sin ( $\omega&space;t$+ 60) A A 50 B 60 C 80 D 100 Answer : A Explanation :
44.
 Determine the total power (in kW)  consumed by a 3-phase delta connected system supplied by a line voltage of  230 V, if the value of phase current is  30 A  and the current lags the voltage by  30 degree. A 14.62 B 15.26 C 16.62 D 17.93 Answer : D Explanation :
45.
 Which of the following bridge is most suitable for the measurement of an unknown resistance A Hay’s Bridge B Anderson Bridge C Wien’s Bridge D Wheatstone Bridge Answer : D Explanation :
46.
 Which of the following instrument is used for the measurement of Insulation resistance A Megger B Wattmeter C Ammeter D Voltmeter Answer : A Explanation :
47.
 What will be the deflection (in rad)  of a moving iron instrument, when the inductance of the moving iron instrument is  (20 +4θ) μH, where θ is the deflection in redian from zero position and the deflection current is  5 A  ? Assuming spring constant k  =  10 × 10- 6 Nm/rad A 5 B 10 C 15 D 20 Answer : A Explanation :
48.
 Determine the value of the unknown capacitance  Cx (in μF)  for the circuit given below, when no current flows through the detector (D) Figure A 20 B 40 C 60 D 80 Answer : B Explanation :
49.
 Which of the given losses are directly proportional to square of speed A Windage loss B Eddy current loss C Both windage and eddy current loss D Hysteresis loss and brush loss Answer : C Explanation :
50.
 Breather is provided in a transformer to A Absorb moisture of air during breathing B Provide cold air in transformer C Absorb moisture from air entering in transformer D Filter the transformer ail. Answer : C Explanation :
51.
 Armature reaction effect is more in A Field weakening method B Armature resistance control C Same in both methods D All option are correct Answer : A Explanation :
52.
 A shunt generator running at  1000 rpm  generated emf of  100 V. If the speed increase to  1200 rpm, the generated emf is A 140 V B 120 V C 240 V D 360 V Answer : B Explanation :
53.
54.
 Which of the following is not a part of transformer A Commutator B Conservator tank C Radiator D Tap changer Answer : A Explanation :
55.
 Find the number of poles required, if the frequency is  50 Hz  and speed of the motor is  500 rpm. A 24 poles B 12 poles C 5 poles D 10 poles Answer : B Explanation :
56.
 In squirrel cage induction, the rotor slots are slight skew in order to reduce A Windage losses B Eddy currents C Reduce magnetic humming effect D Friction losses Answer : C Explanation :
57.
 What type of operate a direct-on-line starter consists of a coil operated A Capacitor operated B A coil operated C Resistor operated D Eddy current operated Answer : B Explanation :
58.
 For a single phase capacitor start induction motor which of the following statements is valid A The capacitor is used for power factor improvement B The direction of rotation can be changed by reversing the main winding terminals C The direction of rotation cannot be changed D The direction of rotation can be changed by interchanging the supply terminals Answer : B Explanation :
59.
 The capacity of single phase induction motor is limited by A Pulsating torque B Uniform torque C Non uniform torque D None of these Answer : A Explanation :
60.
 The function of measurement system  is/are  ________ A Indicating function B Recording function C Controlling function D Indicating, recording and controlling function Answer : D Explanation :
61.
 Which of the following motor will give relatively high starting torque A Capacitor end motor B Capacitor start motor C Split phase motor D Split motor Answer : B Explanation :
62.
 Transmission lines A Absorb reactive power when fully loaded and generate reactive power on light loads B Generate  reactive power when fully loaded and absorb reactive power on light loads C Generate  reactive power on light loads as well as fully loaded D Absorb reactive power on light loads as well as fully loaded Answer : A Explanation :
63.
 Maximum permissible span (in metre)  for wooden poles is A 10 B 20 C 30 D 75 Answer : D Explanation :
64.
 A cable has an insulation of relative permittivity  2.  If the insulation is replaced by one of relative permittivity  4, the capacitance of the cable will become A One fourth B Half C Double D Four times Answer : C Explanation :
65.
 Which insulator is used on dead ends of medium voltage line A Shackle type B Pin type C Egg type D Disc type Answer : A Explanation :
66.
 Which type of fire extinguisher is to be used on electrical equipment or installation under fire A Foam type B Halon type C Gas cartridge water filled type D Stored pressure water filled type Answer : B Explanation :
67.
 What is the unit of luminance A Candela B Lux C Candela / m2 D M2 / candela Answer : C Explanation :
68.
 Determine the power factor of  230V, 0.5 A, 40 W fluorescent lamp A 0.348 B 0.438 C 0.843 D 0.4038 Answer : A Explanation :
69.
 Which type of circuit breaker having higher rating A Miniature circuit breaker B Oil circuit breaker C Air circuit breaker D Vacuum circuit breaker Answer : C Explanation :
70.
 The function of the commutator in  a  DC  machine  is  _________ . A To change alternating current into direct current B To improve commutation C For easy speed control D To change alternating voltage to direct voltage Answer : A Explanation :
71.
 The voltage level of the single phase supply to residential consumer is A 220 V B 210 V C 230 V D 240 V Answer : C Explanation :
72.
 A pin type insulator is made from A Porcelain B Glass C Plastic D All option are correct Answer : D Explanation :
73.
 How will you test the supply in plug point A Tester B Multi-meter C Voltmeter D All option are correct Answer : D Explanation :
74.
 Power factor correction substations consists of A Rectifiers B Inverters C Synchronous condenser D Transformers Answer : C Explanation :
75.
 Energy efficient motors generally have A Longer insulation B Less vibration C Lower heat output D All option are correct Answer : D Explanation :
76.
 Material used for making knife switch is A Nickel B Aluminium C Brass D Nichrome Answer : C Explanation :
77.
 Luminous efficiency of a fluorescent tube is A 5 – 10 lumen / watt B 15 – 20 lumen / watt C 30 – 40 lumen / watt D 60 – 65 lumen / watt Answer : D Explanation :
78.
 A fluorescent tube can be operated on A AC only B DC only C Both AC  as well as  DC D None of these Answer : C Explanation :
79.
 Induction heating process is based on which of the following principles A Thermal ion release principle B Nucleate heating principle C Resistance heating principle D Electromagnetic induction principle Answer : D Explanation :
80.
 A perfect black body is one which A Absorbs all incident radiations B Reflects all incident radiations C Transmits all incident radiations D All option are correct Answer : A Explanation :
81.
 Low frequency supply is obtained by A Motor-generator set B Frequency changer C Either Motor-generator set  or  Frequency changer D Both Motor-generator set  or  Frequency changer Answer : C Explanation :
82.
 A lamp of  500 watts  having Mean spherical candle power  (MSCP) of  1000 is suspended  2.7  metres above the working plane. Calculate illumination directly below the lamp at the working plane A 100.87 lux B 143.83 lux C 137.17 lux D 125.63 lux Answer : C Explanation :
83.
 The impurity added to extrinsic semiconductor is of the order of A 1  in  10 B 1  in  1000 C 1  in  million D 1 in  billion Answer : C Explanation :
84.
 Figure represents a Figure A Zener diode B Silicon controlled rectifier C Tunnel diode D Junction field effect transistor Answer : D Explanation :
85.
 In case of full wave rectifier, the ripple factor is A 1.21 B 0.5 C 0.48 D 1 Answer : C Explanation :
86.
 An amplifier is used to obtain A An increased voltage, current or power of an input signal B Alternation of the input signal C An amplification of frequency response of a communication signal D A distortion less reproduction of radio signals Answer : A Explanation :
87.
 The function of the emitter bypass capacitor in  CE  amplifier is A Provide a low resistance path for the  AC  signals B Provide a high resistance path for the  AC  signals C Act a low resistance path for the  AC  signals D Provide short circuit path for the  DC  signal Answer : A Explanation :
88.
 Synchronizing power of a synchronous machine is A Directly proportional to be synchronous reactance B Equal to the synchronous reactance C Inversely proportional to be synchronous reactance D None of these Answer : C Explanation :
89.
 The normal starting methods that is used to start a synchronous motor is A Star-delta starter B Damper winding C Resistance starter in the armature circuit D Damper winding in conjunction with star-delta starter Answer : D Explanation :
90.
 At what condition synchronous motor can be used as a synchronous capacitor A Under-loaded B Under-excited C Over-loaded D Over-excited Answer : D Explanation :
91.
 Synchronous motor do not have self-starting property because A Starting winding is not provided on the machines B The direction of rotations is not fixed C The direction of instantaneous torque reverses after half cycle D Starters cannot be used on these machines Answer : C Explanation :
92.
 The over-excited synchronous motor takes A Leading current B Lagging current C Both Leading current and  Lagging current D None of these Answer : A Explanation :
93.
 A three-phase synchronous motor will have A One slip-ring B Two slip-ring C No slip-ring D Three slip-ring Answer : B Explanation :