MCQ 770 Questions & Answer Electrical Engineering 2024 Update

MCQ 770 Questions & Answer Electrical Engineering 2024 UpdateMCQ 770 Questions & Answer Electrical Engineering 2024 Update 1. The ratio of voltage and electric current in a closed circuit a. remains constant b. varies c. increases d. falls Ans-c 2. The curve representing ohm's law is a. sine function b. Linear c. a parabola d. a hyperbola Ans-b 3. The resistance of a conductor having length l area of cross section a and resistivity ρ is given as: a. ρa/l b. ρl/a c. ρla d. l/ρ Ans-b 4. The resistance of wire varies inversely as a. area of cross section b. length c. resistivity d. temperature Ans-a 5. Which of the following quantities are same in all parts of a series circuit? a. voltage b. power c. current d. resistance Ans-c 6. Which of the following statements is false in case of a series circuit? a. the voltage drop across each resister is same b. the current flowing through each resistor is the same c. applied voltage is equal to the sum of voltage drops across individual resistors are additive Ans-b 7. A resistance of 30 ohm is connected across 240v supply. If a resistance R ohm is connected in parallel with 30ohm resistor across the same supply, the current drawn becomes triple of original one The unknown resistor R is a. 15ohm b. 10ohm c. 5ohm d.30ohm Ans-a 8. Three resistors, each of R ohms, are connected to form a triangle. The resistance between any two terminals will be: a. 2/3 R b. 3/2R c. R d. 3R Ans-a 9. Which of the following is not correct? a. P=V/R^2 b. P=VI c. I=√ (P/R) d. V=√PR Ans- 10. A 100W bulb is connected in series with a room heater. If now 100W bulb is replaced by a 40w bulb, the heater output will : a. increase b. decrease c. remain the same Ans-b 11. The voltage applied across an electric iron is halved. The power consumption of the iron will be: a. one-half b. one-fourth c. 1/√2times d. three-fourth Ans-b 12. Resistance of 200w,250v lamp will be a. 625ohm b. 1250ohm c.312.5ohm d.31.25ohm Ans-c 13. Two heaters rated at 1000w, 250v each are connected in series across a 250v, 50Hz ac supply. The total power drawn from the supply will be: a. 1000w b. 500w c. 250w d.2000w Ans-b 14. A 200w, 100v lamp is to be operated on 250v supply. The additional resistance required to be connected in series will be: a. 125ohm b. 50ohm c. 75ohm d.25ohm Ans-c 15. Kirchoff's laws are valid for a. linear ckt only b. passive time invariant ckt c. non-linear ckt only d. both linear & non-linear ckt Ans-d 16. KCL is applicable only to a. electric circuits b. electronic circuits c. junctions in a network d. closed loop in a network Ans-c 17. KVL is concerned with a. IR drop b. battery emf c. junction node d. both a and b Ans-c 18. A wye arrangement of resistances has each resistance of 3ohm, the equivalent delta arrangement will have each resistance of values. a. 9ohm b. 6ohm c. 3ohm d. 1ohm Ans-a 19. A battery is connected to a resistance causing a current of 0.5A in the circuit. The current drops to 0.4 when an additional resistance of 5? is connected in series . The current will drop to 0.2A when the resistance is further increased by a. 10 ohm b. 15ohm c. 25ohm d.5 ohm Ans-c 20. Cells are connected in series in order to increase the a. current capacity b. life of the cells c. voltage rating d. terminal voltage Ans-c 21. Cells are connected in parallel in order to increase a. life of the cells b. efficiency c. current capacity d. voltage rating Ans-c 22. When two cells are connected in parallel , it should ensure that have a. identical internal resistances b. equal emfs c. same ampere hour capacity Ans-b 23. The capacity of a battery is expressed in a. amperes b. amperes-hour c. watts d. watt-hour Ans-b 24. A series resonant circuit implies a. zero pf and maximum current b. unity pf and maximum current c. unity pf and minimum current d. zero pf and minimum current Ans-c 25. which one is classified as integrating instrument? a. D'arsonval galvanometer b. ampere-hour meter c. ohm-meter d. ammeter Ans-b 26. Which of the following types of instrument is an integrating instrument? a. power factor meter b. energy meter c. watt meter d. frequency meter Ans-b 27. Voltmeter should be of very high resistance so that a. its range is high b. Its accuracy is high c. it may draw current minimum possible d. its sensitivity is high Ans-c 28. If a voltmeter is connected like a ammeter in series with a load a. the measurement reading will be too high b. Almost no current will flow in the circuit c. the meter will burn out d. an inadmissably high current will flow Ans-b 29. A multirange instrument (ammeter or voltmeter) has a. Multiple shunt or series resistances inside the meter b. variable coil turns c. multi -coil arrangement d. any of the above Ans-a 30. The S.I. unit of power is a. henry b. coulomb c. watt d. watt-hour Ans-c 31. Electric pressure is also called a. resistance b. power c. voltage d. energy Ans-c 32 The substances whfch have a large number of free electrons and offer a low resistance are called a. insulators b. inductors c. semi-conductors d. conductors Ans-d 33. Out of the following which is not a poor conductor ? a. Cast iron b. Copper c. Carbon d. Tungsten Ans-b 34. Out of the following which is an insulating material ? a. Copper b. Gold c. Silver d. Paper Ans-d 35. The property of a conductor due to which it passes current is called a. resistance b. reluctance c. conductance d. inductance Ans-cc 36 . Conductance is reciprocal of (a) resistance (b) inductance (c) reluctance (d) capacitance Ans-a 37. The resistance of a conductor varies inversely as (a) length (b) area of cross-section (c) temperature (d) resistivity Ans-b 38. With rise in temperature the resistance of pure metals (a) Increases (b) decreases (c) first increases and then decreases (d) remains constant Ans-a 39. With rise in temperature the resistance of semi-conductors (a) decreases (b) increases (c) first increases and then decreases (d) remains constant Ans-a 40. The resistance of a copper wire 200 m long is 21 Q. If its thickness (diameter) is 0.44 mm, its specific resistance is around (a) 1.2 x 10~8 Q-m (b) 1.4 x 10~8 Q-m (c) 1.6 x 10""8 Q-m (d) 1.8 x 10"8 Q-m Ans-c 41. Three resistances of 10 ohms, 15 ohms and 30 ohms are connected in parallel. The total resistance of the combination is (a) 5 ohms (b) 10 ohms (c) 15 ohms (d) 55 ohms Ans-a 42. An instrument which detects electric current is known as (a) voltmeter (b) rheostat (c) wattmeter (d) galvanometer Ans-d 43. In a circuit a 33 Q resistor carries a current of 2 A. The voltage across the resistor is (a) 33 V (b) 66 v (c) 80 V (d) 132 V Ans-b 44. A light bulb draws 300 mA when the voltage across it is 240 V. The resistance of the light bulb is (a) 400 ohm (b) 600 ohm (c) 800 ohm (d) 1000 ohm Ans-c 45. The resistance of a parallel circuit consisting of two branches is 12 ohms. If the resistance of one branch is 18 ohms, what is the resistance of the other ? (a) 18 ohm (b) 36 ohm (c) 48 ohm (d) 64 ohm Ans-b 46. Four wires of same material, the same cross-sectional area and the same length when connected in parallel give a resistance of 0.25 ohm. If the same four wires are connected is series the effective resistance will be (a) 1 ohm (b) 2 ohm (c) 3 ohm (d) 4 ohm Ans-d 47. A current of 16 amperes divides between two branches in parallel of resistances 8 ohms and 12 ohms respectively. The current in each branch is (a) 6.4 A, 6.9 A (b) 6.4 A, 9.6 A (c) 4.6 A, 6.9 A (d) 4.6 A, 9.6 A Ans-b 48. Current velocity through a copper conductor is (a) the same as propagation velocity of electric energy (b) independent of current strength (c) of the order of a few micro second (d) nearly 3 x 108 m/s Ans-c 49. Which of the following material has nearly zero temperature co-efficient of resistance? (a) Manganin (b) Porcelain (c) Carbon (d) Copper Ans-a 50. You have to replace 1500 ohm resistor in radio. You have no 1500 ohm resistor but have several 1000 ohm ones which you would connect (a) two in parallel (b) two in parallel and one in series (c) three in parallel (d) three in series Ans-b 51. Two resistors are said to be connected in series 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) sum of IR drops equals the applied e.m.f. Ans-a 52. Which of the following statement is true both for a series and a parallel D.C. circuit? (a) Elements have individual currents (b) Currents are additive (c) Voltages are additive (d) Power are additive Ans-d 53. Which of the following materials has a negative temperature co-efficient of resistance? (a) Copper (b) Aluminum (c) Carbon (d) Brass Ans-c 54. Ohm's law is not applicable to (a) vacuum tubes (b) carbon resistors (c) high voltage circuits (d) circuits with low current densities Ans-a 55. Which is the best conductor of electricity ? (a) Iron (b) Silver (c) Copper (d) Carbon Ans-b 56. For which of the following 'ampere second' could be the unit ? (a) Reluctance (b) Charge (c) Power (d) Energy Ans-b 57. All of the following are equivalent to watt except (a) amperes square ohm (b) joules/sec. (c) amperes x volts (d) amperes/volt Ans-d 58. A resistance having rating 10 ohms, 10W is likely to be a (a) metallic resistor (b) carbon resistor (c) wire wound resistor (d) variable resistor Ans-c 59. Which one of the following does not have negative temperature co-efficient ? (a) Aluminium (b) Paper (c) Rubber (d) Mica Ans-a 60. Varistors are (a) insulators (b) non-linear resistors (c) carbon resistors (d) resistors with zero temperature coefficient Ans-b 61. Insulating materials have the function of (a) preventing a short circuit between conducting wires (b) preventing an open circuit between the voltage source and the load (c) conducting very large currents (d) storing very high currents Ans-a 62. The rating of a fuse wire is always expressed in (a) ampere-hours (b) ampere-volts (c) kWh (d) amperes Ans-d 63. The minimum charge on an ion is (a) equal to the atomic number of the atom (b) equal to the charge of an electron (c) equal to the charge of the number of electrons in an atom zero Ans-b 64. In a series circuit with unequal resistances (a) the highest resistance has the most of the current through it (b) the lowest resistance has the highest voltage drop (c) the lowest resistance has the highest current (d) the highest resistance has the highest voltage drop Ans-c 65. The filament of an electric bulb is made of (a) carbon (b) aluminium (c) tungsten (d) nickel Ans-c 66. A 3 ohm resistor having 2 A current will dissipate the power of (a) 2 watts (b) 4 watts (c) 6 watts (d) 12 watts Ans-d 67. Which of the following statement is true? (a) A galvanometer with low resistance in parallel is a voltmeter (b) A galvanometer with high resistance in parallel is a voltmeter (c) A galvanometer with low resistance in series is an ammeter (d) A galvanometer with high resistance in series is an voltmeter Ans- 68. The resistance of a few metres of wire conductor in closed electrical circuit is (a) practically zero(b) low(c) high (d) very high Ans-a 69. If a parallel circuit is opened in the main line, the current (a) increases in the branch of the lowest resistance (b) increases in each branch (c) is zero in all branches (d) is zero in the highest resistive branch Ans-c 70. If a wire conductor of 0.2 ohm resistance is doubled in length, its resistance becomes (a) 0.4 ohm (b) 0.6 ohm (c) 0.8 ohm (d) 1.0 ohm Ans-a 71. Three 60 W bulbs are in parallel across the 60 V power line. If one bulb burns open (a) there will be heavy current in the main line (b) rest of the two bulbs will not light (c) all three bulbs will light (d) the other two bulbs will light Ans-b 72. The four bulbs of 40 W each are connected in series with a battery across them, which of the following statement is true ? (a) The current through each bulb in same (b) The voltage across each bulb is not same (c) The power dissipation in each bulb is not same (d) None of the above Ans-a 73. Two resistances Rl and R2 are connected in series across the voltage source where R2>R1. The largest drop will be across (a) R2 (b) R1 (c) either Rl or R2 (d) none of them Ans-a 74. What will be energy used by the battery if the battery has to drive 6.28 x 1018 electrons with potential difference of 20 V across the terminal ? (a) 5 joules (b) 10 joules (c) 15 joules (d) 20 joules Ans-d 75. A closed switch has a resistance of (a) zero (b) about 50 ohms (c) about 500 ohms (d) infinity Ans-a 76. The hot resistance of the bulb's filament is higher than its cold resistance because the temperature co-efficient of the filament is (a) zero (b) negative (c) positive (d) about 2 ohms per degree Ans-c 77. Heat in a conductor is produced on the passage of electric current due to (a) reactance (b) capacitance (c) impedance (d) resistance Ans-d 78. The insulation on a current carrying conductor is provided (a) to prevent leakage of current (b) to prevent shock (c) both of above factor (d) none of above factors Ans-c 79. The thickness of insulation provided on the conductor depends on (a) the magnitude of voltage on the conductor (b) the magnitude of current flowing through it (c) both (a) and (b) (d) none of the above Ans-a 80. Which of the following quantities remain the same in all parts of a series circuit ? (a) Voltage (b) Current (c) Power (d) Resistance Ans-b 81. A 40 W bulb is connected in series with a room heater. If now 40 W bulb is replaced by 100 W bulb, the heater output will (a) decrease (b) increase (c) remain same (d) heater will burn out Ans-b 82. In an electric kettle water boils in 10 minutes. It is required to boil the boiler in 15 minutes, using same supply mains (a) length of heating element should be decreased (b) length of heating element should be increased (c) length of heating element has no effect on heating if water (d) none of the above Ans-a 83. An electric filament bulb can be worked from (a) D.C. supply only (b) A.C. supply only (c) Battery supply only (d) All above Ans-d 84. Resistance of a tungsten as applied voltage increases (a) decreases (b) increases (c) remains same (d) none of the above Ans-b 85. Electric current passing through the circuit produces (a) magnetic effect (b) luminous effect (c) thermal effect (d) chemical effect (e) all above effects Ans-c 86. Resistance of a material always decreases if (a) temperature of material is decreased (6) temperature of material is increased (c) number of free electrons available become more (d) none of the above is correct Ans: c 87. If the efficiency of a machine is to be high, what should be low ? (a) Input power (b) Losses (c) True component of power (d) kWh consumed (e) Ratio of output to input Ans: b 88. When electric current passes through a metallic conductor, its temperature rises. This is due to (a) collisions between conduction electrons and atoms (b) the release of conduction electrons from parent atoms (c) mutual collisions between metal atoms (d) mutual collisions between conducting electrons Ans: a 89. Two bulbs of 500 W and 200 W rated at 250 V will have resistance ratio as (a) 4 : 25 (b) 25 : 4 (c) 2 : 5 (d) 5 : 2 Ans: c 90. A glass rod when rubbed with silk cloth is charged because (a) it takes in proton (b) its atoms are removed (c) it gives away electrons (d) it gives away positive charge Ans: c 91. Whether circuit may be AC. or D.C. one, following is most effective in reducing the magnitude of the current. (a) Reactor (b) Capacitor (c) Inductor (d) Resistor Ans: d 92. It becomes more difficult to remove (a) any electron from the (6) first electron from the orbit (c) second electron from the orbit (d) third electron from the orbit Ans: d 93. When one leg of parallel circuit is opened out the total current will (a) reduce (b) increase (c) decrease (d) become zero Ans: c 94. In a lamp load when more than one lamp are switched on the total resistance of the load (a) increases (b) decreases (c) remains same (d) none of the above Ans: b 95. Two lamps 100 W and 40 W are connected in series across 230 V (alternating). Which of the following statement is correct ? (a) 100 W lamp will brighter (b) 40 W lamp will glow brighter (c) Both lamps will glow equally bright (d) 40 W lamp will fuse Ans: b 96. Resistance of 220 V, 100 W lamp will be (a) 4.84 Q (b) 48.4 Q (c) 484 ft (d) 4840 Q Ans: c 97. In the case of direct current (a) magnitude and direction of current remains constant (b) magnitude and direction of current changes with time (c) magnitude of current changes with time (d) magnitude of current remains constant Ans: a 98. When electric current passes through a bucket full of water, lot of bubbling is observed. This suggests that the type of supply is (a) A.C. (b) D.C. (c) any of above two (d) none of the above Ans: b 99. Resistance of carbon filament lamp as the applied voltage increases. (a) increases (b) decreases (c) remains same (d) none of the above Ans: b 100. Bulbs in street lighting are all connected in (a) parallel (b) series (c) series-parallel (d) end-to-end Ans: a 101. For testing appliances, the wattage of test lamp should be (a) very low (b) low (c) high (d) any value Ans: c 102. Switching of a lamp in house produces noise in the radio. This is because switching operation produces (a) arcs across separating contacts (b) mechanical noise of high intensity (c) both mechanical noise and arc between contacts (d) none of the above Ans: a 103. Sparking occurs when a load is switched off because the circuit has high (a) resistance (b) inductance (c) capacitance (d) impedance Ans: b 104. Copper wire of certain length and resistance is drawn out to three times its length without change in volume, the new resistance of wire becomes (a) 1/9 times (b) 3 times (c) 9 times (d) unchanged Ans: c 105. When resistance element of a heater fuses and then we reconnect it after removing a portion of it, the power of the heater will (a) decrease (b) increase (c) remain constant (d) none of the above Ans: b 106. A field of force can exist only between (a) two molecules (b) two ions (c) two atoms (d) two metal particles Ans: b 107. A substance whose molecules consist of dissimilar atoms is called (a) semi-conductor (b) super-conducto (c) compound (d) insulator Ans: c 108. International ohm is defined in terms of the resistance of (a) a column of mercury (b) a cube of carbon (c) a cube of copper (d) the unit length of wire Ans: a 109. 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) 1/3 times (d) 3 times Ans: b 110. Which method can be used for absolute measurement of resistances ? (a) Lorentz method (b) Releigh method (c) Ohm's law method (d) Wheatstone bridge method Ans: d 111. 3 6 ohm resistors are connected to form a triangle. What is the resistance between any two corners ? (a) 3/2 Q (b 6 Q (c) 4 Q (d) 8/3 Q Ans: c 112. Ohm's law is not applicable to (a) semi-conductors (b) D.C. circuits (c) small resistors (d) high currents Ans: a 113. Two copper conductors have equal length. The cross-sectional area of one conductor is four times that of the other. If the conductor having smaller cross-sectional area has a resistance of 40 ohms the resistance of other conductor will be (a) 160 ohms (b) 80 ohms (c) 20 ohms (d) 10 ohms Ans: d 114. A nichrome wire used as a heater coil has the resistance of 2 £2/m. For a heater of 1 kW at 200 V, the length of wire required will be (a) 80 m (b) 60 m (c) 40 m (d) 20 m Ans: a 115. Temperature co-efficient of resistance is expressed in terms of (a) ohms/°C (b) mhos/ohm°C (e) ohms/ohm°C (d) mhos/°C Ans: c 116. Which of the following materials has the least resistivity ? (a) Zinc (b) Lead (c) Mercury (d) Copper Ans: d 117. When current flows through heater coil it glows but supply wiring does not glow because (a) current through supply line flows at slower speed (b) supply wiring is covered with insulation layer (c) resistance of heater coil is more than the supply wires (d) supply wires are made of superior material Ans: c 118. The condition for the validity under Ohm's law is that (a) resistance must be uniform (b) current should be proportional to the size of the resistance (c) resistance must be wire wound type (d) temperature at positive end should be more than the temperature at negative end Ans: a 119. Which of the following statement is correct ? (a) A semi-conductor is a material whose conductivity is same as between that of a conductor and an insulator (b) A semi-conductor is a material which has conductivity having average value of conductivity of metal and insulator (c) A semi-conductor is one which conducts only half of the applied voltage (d) A semi-conductor is a material made of alternate layers of conducting material and insulator Ans: a 120. A rheostat differs from potentiometer in the respect that it (a) has lower wantage rating (b) has higher wattage rating (c) has large number of turns (d) offers large number of tappings Ans: b 121. The weight of an aluminium conductor as compared to a copper conductor of identical cross-section, for the same electrical resistance, is (a) 50% (b) 60% (c) 100% (d) 150% Ans: a 122. An open resistor, when checked with an ohm-meter reads (a) zero (b) infinite (c) high but within tolerance (d) low but not zero Ans: b 123. are the materials having electrical conductivity much less than most of the metals but much greater than that of typical insulators. (a) Varistors (b) Thermistor (c) Semi-conductors (d) Variable resistors Ans: c 124. All good conductors have high (a) conductance (b) resistance (c) reluctance (d) thermal conductivity Ans: a 125. Voltage dependent resistors are usually made from (a) charcoal (b) copper (c) nichrome (d) graphite Ans: c 126. Voltage dependent resistors are used (a) for inductive circuits (6) to supress surges (c) as heating elements (d) as current stabilizers Ans: b 127. The ratio of mass of proton to that of electron is nearly (a) 1840 (b) 1840 (c) 30 (d) 4 Ans: a 128. The number of electrons in the outer most orbit of carbon atom is (a) 3 (b) 4 (c) 6 (d) 7 Ans: b 129. With three resistances connected in parallel, if each dissipates 20 W the total power supplied by the voltage source equals (a) 10 W (b) 20 W (c) 40 W (d) 60 W Ans: d 130. A thermistor has (a) positive temperature coefficient (b) negative temperature coefficient (c) zero temperature coefficient (d) variable temperature coefficient Ans: c 131. If, R and t are the current, resistance and time respectively, then according to Joule's law heat produced will be proportional to (a) I2Rt (b) I2Rf (c) I2R2t (d) I2R2t* Ans: a 132. Nichrome wire is an alloy of (a) lead and zinc (b) chromium and vanadium (c) nickel and chromium (d) copper and silver Ans: c 133. When a voltage of one volt is applied, a circuit allows one microampere current to flow through it.The conductance of the circuit is (a) 1 n-mho (b) 106 mho (c) 1 milli-mho (d) none of the above Ans: a 134. Which of the following can have negative temperature coefficient ? (a) Compounds of silver (6) Liquid metals (c) Metallic alloys (d) Electrolytes Ans: d 135. Conductance : mho :: (a) resistance : ohm (b) capacitance : henry (c) inductance : farad (d) lumen : steradian Ans: a 136. 1 angstrom is equal to (a) 10-8 mm (6) 10"6 cm (c) 10"10 m (d) 10~14 m Ans: c 137. One newton metre is same as (a) one watt (b) one joule (c) five joules (d) one joule second Ans: b 138. The force between two charges is 120 N. If the distance between the charges is doubled, the force will be (a) 60 N (b) 30 N (c) 40 N (d) 15 N Ans: b 139. The electric field intensity at a point situated 4 metres from a point charge is 200 N/C. If the distance is reduced to 2 metres, the field intensity will be (a) 400 N/C (b) 600 N/C (c) 800 N/C (d) 1200 N/C Ans: c 140. The lines of force due to charged particles are (a) always straight(b) always curved (c) sometimes curved(d) none of the above Ans: b 141. The electric field at a point situated at a distance d from straight charged conductor is (a) proportional to d (b) inversely proportional to d (c) inversely proportional to d (d) none of the above Ans: b 142. The direction of electric field due +0 positive charge is . (a) away from the charge (b) towards the charge (c) both (a) and (b) (d) none of the above Ans: a 143. A field line and an equipotential surface are (a) always parallel(b) always at 90° (c) inclined at any angle 0(d) none of the above Ans: b 144. The ability of charged bodies to exert force on 6ne another is attributed to the existence of (a) electrons (b) protons (c) neutrons (d) electric field Ans: d 145. If the sheet of a bakelite is inserted between the of an , the capacitance will (a) decrease (b) increase (c) remains unchanged (d) become zero Ans: b 146. A capacitor stores 0.24 coulombs at 10 volts. Its capacitance is (a) 0.024 F (b) 0.12 F (c) 0.6 F (d) 0.8 F Ans: a 147. For making a capacitor, it is better to select a dielectric having (a) low permittivity (b) high permittivity (c) permittivity same as that of air (d) permittivity slightly more than that of air Ans: b 148. The units of capacitance are (a) volts/coulomb (b) coulombs/volt (c) ohms (d) henry/Wb Ans: b 149. If three 15 uF capacitors are connected in series, the net capacitance is (a) 5 uF (6) 30 uF (c) 45 uF (d) 50 uF Ans: a 150. If three 10 uF capacitors are connected in parallel, the net cararitance is (a) 20 uF (b) 30 uE (c) 40 uF (d) 50 uF Ans: b 151. A dielectric material must be (a) resistor (b) insulator (c) good conductor (d) semi conductor Ans: b 152. An electrolytic capacitor can be used for (a) D.C. only (b) AC. only (c) both D.C. as well as A.C. Ans: a 153. The capacitance of a capacitor is not affected by (a) distance between plates (6) area of plates (c) thickness of plates (d) all of the above Ans: c 154. Which of the following is not a vector ? (a) Linear momentum (b) Angular momentum (c) Electric field (d) Electric potential Ans: b 155. Two plates of a parallel capacitor after being charged from a constant voltage source are separated apart by means of insulated handles, then the (a) Voltage across the plates (b) voltage across the plates decreases (c) charge on the capacitor decreases (d) charge on the capacitor increases Ans: b 156. If A.C. voltage is applied to capacitive circuit, the alternating current can flow in the circuit because (a) varying voltage produces the charging and dicharging currents (b) of high peak value (c) charging current can flow (d) discharge current can flow Ans: a 157. Voltage applied across a ceramic dielectric produces an electrolytic field 100 times greater than air. What will be the value of dielectric constant ? (a) 50 (b) 100 (c) 150 (d) 200 Ans: b 158. Which of the following statements is correct ? (a) Air capacitors have a blackband to indicate the outside foil (6) Electrolytic capacitor must be connected in the correct polarity (c) Ceramic capacitors must be connected in the correct polarity (d) Mica capacitors are available in capacitance value of 1 to 10 pF Ans: b 159. The dissipation factor of a good dielectric is of the order of (a) 0.0002 (b) 0.002 (c) 0.02 (d) 0.2 Ans: a 160. "The total electric flux through any closed surface surrounding charges is equal to the amount oflcharge enclosed".The above statement is associated with (a) Coulomb's square law (b) Gauss's law (c) Maxwell's first law (d) Maxwell's second law Ans: b 161. Three capacitors each of the capacity C are given. The resultant capacity 2/3 C can be obtained by using them (a) all in series (b) all in parallel (c) two in parallel and third in series with this combination (d) two in series and third in parallel across this combination Ans: c 162. For which of the following parameter variation, the capacitance of the capacitor remains unaffected ? (a) Distance between plates (b) Area of the plates (c) Nature of dielectric (d) Thickness of the plates Ans: d 163. Which of the following statement is true ? (a) The current in the discharging capacitor grows linearly (b) The current in the dicharging capacitor grows exponentially (c) The current in the discharging capacitor decays exponentially (d) The current in the discharging capacitor decreases constantly Ans: b 164. Which of the following expression is correct for electric field strength ? (a) E = D/E (b) E = D2/t (c) E = jtD (d) E= nD2 Ans: a 165. In a capacitor the electric charge is stored in (a) metal plates (b) dielectric (c) both (a) and (6) (d) none of the above Ans: b 166. Which of the following materials has the highest value of dielectric constant? (a) Glass (b) Vacuum (c) Ceramics (d) Oil Ans: c 167. Which of the following capacitors will have the least variation ? (a) Paper capacitor (b) Ceramic capacitor (c) Silver plated mica capacitor (d) None of the above Ans: c 168. Which of the following statements is incorrect ? (a) The leakage resistance of ceramic capacitors is generally high (b) The stored energy in a capacitor decreases with reduction in value of capacitance (c) The stored energy in a capacitor increases with applied voltage (d) A wire cable has distributed capacitance between the conductors Ans: b 169. Which of the following capacitors has relatively shorter shelf life ? (a) Mica capacitor (b) Electrolytic capacitor (c) Ceramic capacitor (d) Paper capacitor Ans: b 170. The sparking between two electrical contacts can be reduced by inserting a (a) capacitor in parallel with contacts (6) capacitor in series with each contact (c) resistance in line (d) none of the above Ans: a 171. In the case of a lossy capacitor, its series equivalent resistance value will be (a) small (b) very small (c) large (d) zero Ans: c 172. The power dissipated in a pure capacitor is (a) zero (6) proportional to applied voltage (c) proportional to value of capacitance (d) both (b) and (c) above Ans: a 173. In a capacitive circuit (a) a steady value of applied voltage causes discharge (b) an increase in applied voltage makes a capacitor charge (c) decrease in applied voltage makes a capacitor charge (d) none of the above Ans: b 174. When a dielectric slab is introduced in a parallel plate capacitor, the potential difference between plates will (a) remain uncharged (b) decrease (c) increase (d) become zero Ans: b 175. Capacitance increases with (a) increase in plate area and decrease in distance between the plates (b) increase in plate area and distance between the plates (c) decrease in plate area and value of applied voltage (d) reduction in plate area and distance between the plates Ans: a 176. A capacitor consists of (a) two insulators separated by a conductor (b) two conductors separated by an insulator (c) two insulators only (d) two conductors only Ans: b 177. A paper capacitor is usually available in the form of (a) tubes (b) rolled foil (c) disc (d) meshed plates Ans: b 178. Air capacitors are generally available in the range (a) 10 to 400 pF (b) 1 to 20 pF (c) 100 to 900 pF (d) 20 to 100 pF Ans: a 179. The unit of capacitance is (a) henry (b) ohm (c) farad (d) farad/m Ans: c 180. A capacitor charged to 200 V has 2000 (iC of charge. The value of capacitance will be (a) 10 F (6) 10 uF (c) 100 nF (d) 1000 uF Ans: b 181. A capacitor in a circuit became hot and ultimately exploded due to wrong connections, which type of capacitor it could be ? (a) Paper capacitor (b) Ceramic capacitor (c) Electrolytic capacitor (d) Any-of the above Ans: c 182. Energy stored in the electric field of a capacitor C when charged from a D.C source of voltage V is equal to joules (a) CV2 (b) C2V (c) CV2 (d) CV Ans: a 183. The absolute permittivity of free space is given by (a) 8.854 x 1(T9 F/m) (6) 8.854 x 1(T10 F/m) (c) 8.854 x KT11 F/m (d) 8.854 x 10"12 F/m Ans: b 184. The relative permittivity of free space is given by (a) 1 (b) 10 (c) 100 (d) 1000 Ans: a 185. Electric field intensity is a quantity (a) scalar (b) vector (c) both (a) and (6) (d) none of the above Ans: b 186. When 4 volts e.m.f. is applied across a 1 farad capacitor, it will store energy of (a) 2 joules (b) 4 joules (c) 6 joules (d) 8 joules Ans: d 187. The capacitor preferred for high circuits is (a) air capacitor (b) mica capacitor (c) electrolytic capacitor (d) none of the above Ans: b 188. The capacity of capacitor bank used in power factor correction is expressed in terms of (a) kW (b) kVA (c) kVAR (d) volts Ans: c 189. While testing a capacitor with ohm-metre, if the capacitor shows charging, but the final resistance reading is appreciably less than normal, it can be concluded that the capacitor is (a) short-circuited (b) open circuited (c) alright (d) leaky Ans: d 190. If a 6 mF capacitor is charged to 200 V, the charge in coulombs will be (a) 800 uC (b) 900 uC (c) 1200 uC (d) 1600 uC Ans: c 191. Which capacitor will be physically smaller for the same ratings ? (a) Ceramic capacitor (b) Paper capacitor (c) Both will be of equal size (d) None of the above Ans: a 192. What is the value of capacitance that must be connected in parallel with 50 pF condenser to make an equivalent capacitance of 150 pF ? (a) 50 pF (b) 100 pF (c) 150 pF (d) 200 pF Ans: b 193. A mica capacitor and a ceramic capacitor both have the same physical dimensions. Which will have more value of capacitance ? (a) Ceramic capacitor (b) Mica capacitor (c) Both will have identical value of capacitance (d) It depends on applied voltage Ans: a 194. Which of the following material has least value of dielectric constant ? (a) Ceramics (b) Oil (c) Glass (d) Paper Ans: b 195. Which of the following capacitors will have the least value of breakdown voltage ? (a) Mica (b) Paper (c) Ceramic (d) Electrolytic Ans: d 196. The breakdown voltage for paper capacitors is usually (a) 20 to 60 volts (b) 200 to 1600 volts (c) 2000 to 3000 volts (d) more than 10000 volts Ans:b 197. Dielectric constant for mica is nearly (a) 200 (b) 100 (c) 3 to 8 (d) 1 to 2 Ans: c 198. The value of dielectric constant for vacuum is taken as (a) zero (b) 1 (c) 4 (d) 10 Ans: b 199. Which of the following capacitors is marked for polarity ? (a) Air (b) Paper (c) Mica (d) Electrolytic Ans: d 200. Which of the following capacitors can be used for temperature compensation ? (a) Air capacitor (b) Ceramic capacitor (c) Paper capacitor (d) None of the above Ans: b 201. Which of the following statements is incorrect ? (a) The thinner the dielectric, the more the capacitance and the lower the voltage breakdown rating for a capacitor . (b) A six dot mica capacitor colour coded white, green, black, red and yellow has the capacitance value of 500 pF (c) Capacitors in series provide less capacitance but a higher voltage breakdown rating for the combination (d) A capacitor can store charge because it has a dielectric between two conductors Ans: b 202. Paper capacitors usually have a tolerance of (a) ± 5% (b) ± 10% (c) ± 15% (d) ± 20% Ans: b 203. For closer tolerances which of the following capacitors is usually preferred ? (a) Paper capacitor (b) Mica capacitor (c) Ceramic disc capacitor (d) None of the above Ans: b 204. The electrostatic force between two charges of one coulomb each and placed at a distance of 0.5 m will be (a) 36 x 10fa (b) 36 x 107 N (c) 36 x 108 N (d) 36 x 109 N Ans: d 205. The units of volume charge density are (a) Coulomb/metre (b) Coulomb/metre (c) Coulomb/metre (d) Coulomb/metre Ans: c 206. "The surface integral of the normal component of the electric displacement D over any closed surface equals the charge enclosed by the surface". The above statement is associated with (a) Gauss's law (b) Kirchhoff s law (c) 's law (d) Lenz's law Ans: a 207. Dielectric strength of mica is (a) 10 to 20 kV/mm (6) 30 to 50 kV/mm (c) 50 to 200 kV/mm (d) 300 to 500 kV/mm Ans: c 208. The dielectric constant (relative permittivity) of glass is given by (a) 0.1 to 0.4 (b) 0.5 to 1.0(c) 2.0 to 4.0 (d) 5 to 100 Ans: d 209 capacitors are mainly used for radio frequency tuning. (a) Paper (b) Air (c) Mica (d) Electrolytic Ans: b 210. capacitors can be used only for D.C. (a) Air (b) Paper (c) Mica (d) Electrolytic Ans: d 211. capacitors are used in transistor circuits. (a) Ceramic (b) Paper (c) Air (d) Electrolytic Ans: a 212. capacitors are used for audio frequency and radio frequency coupling and tuning. (a) Air (b) Mica (c) Plastic film (d) Ceramic Ans: b 213. The inverse of capacitance is called (a) reluctance (b) conductance (c) susceptance (d) elastance Ans: d 214. When the dielectric is homogeneous,the potential gradient is (a) uniform (b) non-uniform (c) zero (d) any of the above Ans: a 215. The potential gradient across the material of low permittivity is than across the material of high permittivity. (a) smaller (b) greater (c) both (a) and (b) (d) none of the above Ans: b 216. field is associated with the capacitor. (a) Electric (b) Magnetic (c) Both (a) and (b) (d) None of the above Ans: a 217. A capacitor having capacitance of 5 uF is charged to a potential difference of 10,000 V. The energy stored in the capacitor is (a) 50 joules (b) 150 joules (c) 200 joules (d) 250 joules Ans: d 218. A single core cable used on 33000 V has conductor diameter 10 mm and the internal diameter of sheath 25 mm. The maximum electrostatic stress in the cable is (a) 62 x 105 V/m (b) 72 x 105 V/m (c) 82 x 105 V/m (d) 92 x 105 V/m Ans: b 219. Two infinite parallel plates 10 mm apart have maintained between them a potential difference of 100 V. The acceleration of an electron placed between them is (a) 0.56 x 1015 m/s2 (b) 1.5 x 1015 m/s2 (c) 1.6 x 1015 m/s2 (d) 1.76 x 1015 m/s2 Ans: d 220. The total deficiency or excess of electrons in a body is known as (a) current (b) voltage (c) potential gradient (d) charge Ans: d 221. The relative permittivity has the following units (a) F/m (b) m/F (c) Wb/m (d) no units Ans: c 222. The phenomenon of an uncharged body getting charged merely by the nearness of a charged body is known as (a) pholoelectric effect (b) chemical effect (c) magnetic effect (d) induction Ans: d 223. A unit tube of flux is known as tube (a) Newton (b) Faraday (c) Michale (d) None of the above Ans: b 224. The number of Faraday tubes of flux passing through a surface in an electric field is called (a) electric flux (6) electric flux density (c) magnetic flux density (d) electric charge density Ans: a 225. The unit of electric intensity is (a) N/C2 (b) Wb/m2 (c) N/C (d) N2/C Ans:c 226. The value of E within the field due to a point charge can be found with the help of (a) Faraday's laws (b) Kirchhoff s laws (c) Coulomb's laws (d) none of the above Ans: c 227. at a point may be defined as equal to the lines of force passing normally through a unit cross section at that point. (a) Electric intensity (6) Magnetic flux density (c) Electric flux (d) None of the above Ans: a 228. Electric intensity at any point in an electric field is equal to the at that point. (a) electric flux (b) magnetic flux density (c) potential gradient (d) none of the above Ans: c 229. Electric displacement is a quantity. (a) scalar (b) vector (c) both of the above (d) none of the above Ans: b 230. at a point is equal to the negative potential gradient at that point. (a) Electric intensity (6) Electric flux (c) Magnetic flux (d) Magnetic flux density Ans: a 231. The unit of dielectric strength is given by (a) V/m (b) V2/m (c) m/V (d) m/V2 Ans: a 232. Dielectric strength with increasing thickness (a) increases (b) decreases (c) remains unaltered (d) none of the above Ans: b 233. The property of a capacitor to store electricity is called its (a) capacitance (b) charge (c) energy (d) none of the above Ans: a 234. is that property of a capacitor which delays any change of voltage across it. (a) Inductance (b) Capacitance (c) Potential gradient (d) None of the above Ans: b 235. A capacitance of 100 pF is connected in series with a resistance of 8000 ohm. The time constant of the circuit is (a) 0.2 s (b) 0.4 s (c) 0.6 s (d) 0.8 s Ans: d 236. In a cable capacitor, voltage gradient is maximum at the surface of the (a) earth (b) conduction (c) sheath (d) insulator Ans: b 237. The time constant of an R-C circuit is defined as the time during which capacitor charging voltage actually rises to _ percent of its value. (a) 37, initial (b) 63.2, initial (c) 63.2, final (d) 37, final Ans: c 238. The time constant and R-C circuit may also be defined as the time during which the charging current falls to percent of its initial maximum value, (a) 37 (b) 42 (c) 63 (d) 73 Ans: a 239. The capacitance of a capacitor is influenced by (a) plate area (b) plate separation (c) nature of dielectric (d) none of the above (e) all of the above Ans:e 240. A capacitor consists of two (a) ceramic plates and one mica disc (b) insulators separated by a dielectric (c) silver-coated insulators (d) conductors separated by an insulator Ans: d 241. Permittivity is expressed in (a) Farad/sq-m (b) Farad/metre (c) Weber/metre (d) Weber/sq-m Ans: b 242. Dielectric strength of a material depends on (a) moisture content (b) temperature (c) thickness (d) all of the above (e) none of the above Ans: d 243. What will happen to an insulating medium if voltage more than the breakdown voltage is applied on it ? (a) It will become magnetic (b) It will melt (c) It will get punctured or cracked (d) Its molecular structure will get changed Ans: c 244. Which medium has the least dielectric strength ? (a) Paraffin wax (b) Quartz (c) Glass (d) Air Ans: d 245. 1 volt/metre is same as (a) 1 metre/coulomb(6) 1 newton metre(c) 1 newton/metre(d) 1 joule/coulomb Ans: c 246. One volt is the same as (a) one joule/coulomb (b) one coulomb/joule (c) one coulomb (d) one joule Ans: a 247. The capacitance between two plates increases with (a) shorter plate area and higher applied voltage (6) shorter plate area and shorter distance between them (c) larger plate area, longer distance between plates and higher,applied voltage (d) larger plate area and shorter distance between plates Ans: d 248. The capacitance C is charged through a resistance R. The time constant of the charging circuit is given by (a) CIR (b) 1/RC (c) RC (d) RIC Ans: c 249. The bridge used for the measurement of the value of the capacitance is (a) Wien's bridge (b) Wheatstone bridge (c) Schering bridge (d) Hay's bridge Ans: c 250. If an ohmmeter reading immediately goes practically to zero and stays there, capacitor is (a) charged (b) short-circuited (c) lossy (d) satisfactory Ans: b 251. Out of the following capacitors of identical rating which one will have the smallest dimensions ? (a) Aluminium foil capacitor (b) Mica capacitor (c) Ceramic capacitor (d) Paper capacitor Ans: c 252. An uncharged conductor is placed near a charged conductor, then (a) the uncharged conductor gets charged by conduction (6) the uncharged conductor gets charged by induction and then attracted towards the charging body (c) the uncharged conductor is attracted first and then charged by induction (d) it remains as such Ans: b 253. The presence of an uncharged conductor near a charged one increases the (a) charge of the charged conductor (6) capacity of the charged conductor (c) potential of the charged conductor (d) all of the above Ans: b 254. Paper condenser is (a) always polarised (6) usually of fixed value (c) electrolytic condenser (d) a variable condenser Ans: b 255. Mica capacitors are characterised by all of thte following except (a) stable operation (b) accurate value (c) low leakage reactance (d) low losses Ans: c 256. A potential of 400 V is applied to a capacitor, the plates of which are 4 mm apart. The strength of electric field is (a) 100 kV/m (b) 10 kV/m (c) 5 kV/m (d) 2 kV/m Ans: a 257. For a good 0.05 uF capacitor ohmmeter reading should (a) show low resistance momentarily and back off to a very high resistance (6) show high resistance momentarily and then a very low resistance (c) go quickly to 50 ohm approximately and remain there (d) not move at all Ans: a 258. The ohmmeter reading for a short circuited capacitor is (a) infinity (b) few kilo ohms (c) few megaahms (d) zero Ans: d 259. Which of the following statements is correct ? (a) Mica capacitors are available in capacitance values of 5 to 20 iF (b) Air capapitors have a black band to indicate the outside foil (c) Electrolytic capacitors must be connected in correct polarity (d) Ceramic capacitors must be connected in correct polarity Ans: c 260. Which of the following capacitors preferred for high frequency circuits ? (a) Air capacitor (b) Electrolytic capacitor (c) Mica capacitor (d) none of the above Ans: c 261. An electrolytic capacitor is generally made to provide (a) low capacitance (b) fixed capacitance (c) variable capacitance (d) large value of capacitance Ans: d 262. In order to remove static electricity from machinery (a) construct insulated cabins (b) insulate the machinery (c) ground the framework (d) humidify the surroundings Ans: c 263. If a third equal and similar charge is placed between two equal and similar charges, then this third charge will (a) move out of the field of influence of the two charges (b) remain in stable equilibrium (c) not be in equilibrium (d) be in unstable equilibrium Ans: b 264. A region around a stationary electric charge has (a) an electric field (b) a magnetic field (c) both (a) and (b) (d) none of the above Ans: a 265. The minimum value of potential gradient in a cable occurs in (a) insulation (b) conductor (c) outer sheath (d) uniformly all over Ans: a 266. Dielectric strength of medium (a) increases with rise in temperature (b) increases with moisture content (c) is same for all insulating materials (d) none of the above Ans: d 267. Acharge which when placed in vacuum from an equal and similar charge repels with a force of 9 x 10 N, is known as (a) milli-coulomb (b) micro-coulomb (c) pico-coulomb (d) coulomb Ans: b 268. Dielectric strength of a medium is usually expressed in (a) J/mm (b) C/m2 (c) kV/mm (d) N/mm Ans: c 269. A positive and a negative charge are initially 50 mm apart. When they are moved close together so that they are now only 10 mm apart, the force between them will be (a) 5 times smaller than before (b) 5 times greater than before (c) 10 times greater than before (d) 25 times larger than before Ans: d 270. Which is the most superior dielectric out of the following ? (a) Air (b) Glass (c) Bakelite (d) Paper Ans: c 271. When a dielectric is placed in an electric field the field strength (a) decreases (b) increases (c) reduces to zero (d) remain unchanged Ans: a 272. To prevent the generation of static charges on rubber or flat leather (a) surface is moistened (b) conductive dressing is done (c) oil compound dressing is done (d) talcum powder is sprayed on the surface Ans: b 273. Which of the following capacitor is preferred in case of single phase motor ? (a) Mica capacitor (b) Paper capacitor (c) Electrolytic capacitor (d) Ceramic capacitor Ans: c 274. A capacitance is a circuit component that opposes the change in circuit (a) current (b) voltage (c) impedance (d) none of the above Ans: a 275. A condenser suitable for D.C. only is (a) metallic plate variable gang condenser (b) metallic paper capacitor (c) oil impregrated paper condenser (d) poled aluminium electrolytic condenser Ans: d 276. In a capacitor, the electric charge is stored in (a) metal plates (b) dielectric (c) dielectric as well as metal plates (d) none of the above Ans: b 277. An air gap is usually inserted in magnetic circuits to (a) increase m.m.f. (b) increase the flux (c) prevent saturation (d) none of the above Ans: c 278. The relative permeability of a ferromagnetic material is (a) less than one (b) more than one (c) more than 10 (d) more than 100 or 1000 Ans: d 279. The unit of magnetic flux is (a) henry (b) weber (c) ampereturn/weber (d) ampere/metre Ans: b 280. Permeability in a magnetic circuit corresponds to in an electric circuit. (a) resistance (b) resistivity (c) conductivity (d) conductance Ans: c 281. Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it (a) lowers their power efficiency (b) increases their cost of (c) leads to their increased weight (d) produces fringing Ans: a 282. Relative permeability of vacuum is (a) 1 (b) 1 H/m (c) 1/4JI (d) 4n x 10-' H/m Ans: a 283. Permanent magnets are normally made of (a) alnico alloys (b) aluminium (c) cast iron (d) wrought iron Ans: a 284. Energy stored by a coil is doubled when its current is increased by percent. (a) 25(b) 50 (c)41.4 (d) 100 Ans: c 285. Those magnetic materials are best suited for making armature and transformer cores which have permeability and hystersis loss. (a) high, high (b) low, high (c) high, low (d) low, low Ans: c 286. The rate of rise of current through an inductive coil is maximum (a) at 63.2% of its maximum steady value (b) at the start of the current flow (c) after one time constant (d) near the final maximum value of current Ans: b 287. When both the inductance and resistance of a coil are doubled the value of (a) time constant remains unchanged (b) initial rate of rise of current is doubled (c) final steady current is doubled (d) time constant is halved Ans: a 288. The initial rate of rise of current through a coil of inductance 10 H when suddenly connected to a D.C. supply of 200 V is Vs (a) 50 (b) 20 (c) 0.05 (d) 500 Ans: b 289. A material for good magnetic memory (a) low hysteresis loss (b) high permeability (c) low retentivity (d) high retentivity Ans: d 290. Conductivity is analogous to (a) retentivity (b) resistivity (c) permeability (d) inductance Ans: c 291. In a magnetic material hysteresis loss takes place primarily due to (a) rapid reversals of its magnetization (b) flux density lagging behind magnetising force (c) molecular friction (d) it high retentivity Ans: d 292. Those materials are well suited for making permanent magnets which have retentivity and coercivity. (a) low, high (b) high, high (c) high, low (d) low, low Ans: b 293. If the area of hysteresis loop of a material is , the hysteresis loss in this material will be (a) zero (b) small (c) large (d) none of the above Ans: c 294. Hard steel is suitable for making permanent magnets because (a) it has good residual magnetism (b) its hysteresis loop has large area (c) its mechanical strength is high (d) its mechanical strength is low Ans: a 295. Silicon steel is used in electrical machines because it has (a) low co-ercivity (b) low retentivity (c) low hysteresis loss (d) high co-ercivity Ans: c 296. Conductance is analogous to (a) permeance (b) reluctance (c) flux (d) inductance Ans: a 297. The property of a material which opposes the creation of magnetic flux in it is known as (a) reluctivity (b) magnetomotive force (c) permeance (d) reluctance Ans: d 298. The unit of retentivity is (a) weber (b) weber/sq. m (c) ampere turn/metre (d) ampere turn Ans: b 299. Reciprocal of reluctance is (a) reluctivity (b) permeance (c) permeability (d) susceptibility Ans: b 300. While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electrical circuit ? (a) E.m.f. (b) Current (c) Current density (d) Conductivity Ans: b 301. The unit of reluctance is (a) metre/henry (b) henry/metre (c) henry (d) 1/henry Ans: d 302. A ferrite core has less eddy current loss than an iron core because (a) ferrites have high resistance (b) ferrites are magnetic (c) ferrites have low permeability (d) ferrites have high hysteresis Ans: d 303. Hysteresis loss least depends on (a) volume of material (b) frequency (c) steinmetz co-efficient of material(d) ambient temperature Ans: d 304. Laminated cores, in electrical machines, are used to reduce (a) copper loss (b) eddy current loss (c) hysteresis loss (d) all of the above Ans: b 305. "The mass of an ion liberated at an electrode is directly proportional to the quantity of electricity".The above statement is associated with (a) Newton's law (b) Faraday's law of electromagnetic (c) Faraday's law of electrolysis (d) Gauss's law Ans: c 306. The charge required to liberate one gram equivalent of any substance is known as constant (a) time (b) Faraday's (c) Boltzman Ans: b 307. During the charging of a lead-acid cell (a) its voltage (b) it gives out energy (c) its cathode becomes dark chocolate brown in colour (d) specific gravity of H2SO4 decreases Ans: a 308. The capacity of a lead-acid cell does not depend on its (a) temperature (b) rate of charge (c) rate of discharge (d) quantity of active material Ans: b 309. During charging the specific gravity of the electrolyte of a lead-acid battery (a) increases (b) decreases (c) remains the same (d) becomes zero Ans: a 310. The active materials on the positive and negative plates of a fully charged lead-acid battery are (a) lead and lead peroxide (b) lead sulphate and lead (c) lead peroxide and lead (d) none of the above Ans: c 310. When a lead-acid battery is in fully charged condition, the colour of its positive plate is (a) dark grey (b) brown (c) dark brown (d) none of above Ans: c 311. The active materials of a nickel-iron battery are (a) nickel hydroxide (6) powdered iron and its oxide (c) 21% solution of KOH (d) all of the above Ans: d 312. The ratio of ampere-hour efficiency to watt-hour efficiency of a lead-acid cell is (a) just one (b) always greater than one (c) always less than one (d) none of the above. Ans: b 313. The best indication about the state of charge on a lead-acid battery is given by (a) output voltage (b) temperature of electrolyte (c) specific gravity of electrolyte (d) none of the above Ans: c 314. The storage battery generally used in electric power station is (a) nickel-cadmium battery (b) zinc-carbon battery (c) lead-acid battery (d) none of the above Ans: c 315. The output voltage of a charger is (a) less than the battery voltage (b) higher than the battery voltage (c) the same as the battery voltage (d) none of the above Ans: b 316. Cells are connected in series in order to (a) increase the voltage rating (6) increase the current rating (c) increase the life of the cells (d) none of the above Ans: a 317. Five 2 V cells are connected in parallel.The output voltage is (a) 1 V (6) 1.5 V (c) 1.75 V (d) 2 V Ans: d 318. The capacity of a battery is expressed in terms of (a) current rating (b) voltage rating (e) ampere-hour rating (d) none of the above Ans: c 319. Duringthe charging and discharging of a nickel-iron cell (a) corrosive fumes are produced (b) water is neither formed nor absorbed (c) nickel hydroxide remains unsplit (d) its e.m.f. remains constant Ans: b 320. As compared to constant-current system, the constant-voltage system of charging a lead acid cell has the advantage of (a) reducing time of charging (b) increasing cell capacity (c) both (a) and (b) (d) avoiding excessive gassing Ans: c 321. A dead storage battery can be revived by (a) adding (6) adding so-called battery restorer (c) a dose of H2SO4 (d) none of the above Ans: d 322. As compared to a lead-acid cell, the efficiency of a nickel-iron cell is less due to its (a) compactness (b) lower e.m.f. (c) small quantity of electrolyte used (d) higher internal resistance Ans: d 323. Trickle charging of a storage battery helps to (a) maintain proper electrolyte level (b) increase its reserve capacity (c) prevent sulphation (d) keep it fresh and fully charged Ans: d 324. Those substances of the cell which take active part in chemical combination and hence produce electricity during charging or discharging are known as materials. (a) passive (b) active (c) redundant (d) inert Ans: b 325. In a lead-acid cell dilute sulphuric acid (electrolyte) approximately comprises the following (a) one part H2O, three parts H2SO4 (b) two parts H2O, two parts H2SO4 (c) three parts H2O, one part H2SO4 (d) all H2S04 Ans: c 326. It is noticed that durmg charging (a) there is a rise in voltage (6) energy is absorbed by the cell (c) specific gravity of H2SO4 is increased (d) the anode becomes chocolate brown in colour (PbCfe) and cathode becomes grey metallic lead (Pb) (e) all of the above Ans: e 327. It is noticed that during discharging the following does not happen (a) both anode and cathode become PbS04 (b) specific gravity of H2SO4 decreases (c) voltage of the cell decreases (d) the cell absorbs energy Ans: d 328. The ampere-hour efficiency of a leadacid cell is normally between (a) 20 to 30% (b) 40 to 50% (c) 60 to 70% (d) 90 to 95% Ans: d 329. The watt-hour efficiency of a lead-acid cell varies between (a) 25 to 35% (b) 40 to 60% (c) 70 to 80% (d) 90 to 95% Ans: c 330. The capacity of a lead-acid cell is measured in (a) amperes (b) ampere-hours (c) watts (d) watt-hours Ans: b 331. The capacity of a lead-acid cell depends on (a) rate of discharge (b) temperature (c) density of electrolyte (d) quantity of active materials (e) all above Ans: e 332. When the lead-acid cell is fully charged, the electrolyte assumes _ appearance (a) dull (b) reddish (c) bright (d) milky Ans: d 333. The e.m.f. of an Edison cell, when fully charged, is nearly (a) 1.4 V (b) 1 V (c) 0.9 V (d) 0.8 V Ans: a 334. The internal resistance of an alkali cell is nearly times that of the lead- acid cell. (a) two (b) three (c) four (d) five Ans: d 335. The average charging voltage for alkali cell is about (a) 1 V (b) 1.2 V (c) 1.7 V (d) 2.1 V Ans: c 336. On the average the ampere-hour efficiency of an Edison cell is about (a) 40% (b) 60% (c) 70% (d) 80% Ans: d 337. The active material of the positive plates of silver-zinc batteries is (a) silver oxide (b) lead oxide (c) lead (d) zinc powder Ans: a 338. Lead-acid cell has a life of nearly charges and discharges (a) 500 (b) 700 (c) 1000 (d) 1250 Ans: d 339. Life of the Edison cell is at least (a) five years (b) seven years (c) eight years (d) ten years Ans: a 340. The internal resistance of a lead-acid cell is that of Edison cell (a) less than (b) more than (c) equal to (d) none of the above Ans: a 341. Electrolyte used in an Edison cell is (a) NaOH (b) KOH (c) HC1 (d) HN03 Ans: b 342. Electrolyte used in a lead-acid cell is (a) NaOH (b) onlyH2S04 (c) only water (d) dilute H2SO4 Ans: d 343. Negative plate of an Edison cell is made of (a) copper (b) lead (c) iron (d) silver oxide Ans: c 344. The open circuit voltage of any storage cell depends wholly upon (a) its chemical constituents (b) on the strength of its electrolyte (c) its temperature (d) all above Ans: d 345. The specific gravity of electrolyte is measured by (a) manometer (6) a mechanical gauge (c) hydrometer (d) psychrometer Ans: c 346. When the specific gravity of the electrolyte of a lead-acid cell is reduced to 1.1 to 1.15 the cell is in (a) charged state (b) discharged state (c) both (a) and (b) (d) active state Ans: b 347. In system the charging current is intermittently controlled at either a maximum or minimum value (a) two rate charge control (b) trickle charge (c) floating charge (d) an equalizing charge Ans: a 348. Over charging (a) produces excessive gassing (b) loosens the active material (e) increases the temperature resulting in buckling of plates (d) all above Ans: d 349. Undercharging (a) reduces specific gravity of the electrolyte (b) increases specific gravity of the electrolyte (c) produces excessive gassing (d) increases the temperature Ans: a 350. Internal short circuits are caused by (a) breakdown of one or more separators (b) excess accumulation of sediment at the bottom of the cell (c) both (a) and (b) (d) none of the above Ans: c 351. The effect of sulphation is that the internal resistance (a) increases (b) decreases(c) remains same (d) none of the above Ans: a 352. Excessive formation of lead sulphate on the surface of the plates happens because of (a) allowing a battery to stand in discharged condition for a long time (b) topping up with electrolyte (c) persistent undercharging (d) low level of electrolyte (e) all above Ans: e 353. The substances which combine together to store electrical energy during the charge are called materials (a) active (b) passive (c) inert (d) dielectric Ans: a 354. In a lead-acid cell, lead is called as (a) positive active material (b) negative active material (c) passive material (d) none of the above Ans: b 355. The lead-acid cell should never be discharged beyond (a) 1.8 V (b) 1.9 V (c) 2 V (d) 2.1 V Ans: a 356. On overcharging a battery (a) it will bring about chemical change in active materials (b) it will increase the capacity of the battery (c) it will raise the specific gravity of the electrolyte (d) none of the above will occur Ans: d 357. Each cell has a vent cap (a) to allow gases out when the cell is on charge (b) to add water to the cell if needed (c) to check the level of electrolyte (d) to do all above functions Ans: d 358. Following will occur if level of electrolyte falls below plates (a) capacity of the cell is reduced (b) life of the cell is reduced (c) open plates are converted to lead sulphate (d) all above Ans: d 359. In constant voltage charging method, the charging current from discharged to fully charged condition (a) decreases (b) increases (c) remains constant (d) none of the above Ans: a 360. 48 ampere-hour capacity would deliver a current of (a) 48 amperes for 1 hour (b) 24 amperes for 2 hours (c) 8 amperes for 6 hours (d) 6 amperes for 8 hours Ans: d 361. In constant-current charging method, the supply voltage from discharged to fully charged condition (a) decreases (b) increases (c) remains constant (d) none of the above Ans: b 362. Battery charging equipment is generally installed (a) in well ventilated location (b) in clean and place (c) as near as practical to the battery being charged (d) in location having all above features Ans: d 363. Following will happen if the specific gravity of electrolyte becomes more than 1.23. (a) Loss of capacity (b) Loss of life (c) Corrosion of the grids of the plate (d) All above Ans: d 364. Batteries are charged by (a) rectifiers (b) engine generator sets (c) motor generator sets (d) any one of the above methods Ans: d 365. Cell short circuit results in (a) low sp. gravity electrolyte (b) abnormal high temperature (c) reduced gassing on charge (d) all above Ans: d 366. Internal resistance of a cell is reduced by (a) using vent plug to permit gas formed during discharge (b) increasing the plate area (c) putting plates very close together (d) all above methods Ans: d 367. Capacity of dry cells is (a) more when it is supplying current for intermittent periods (b) more when it is supplying current for continuous periods (c) unaffected by the type of discharge (d) none of the above Ans: a 368. Battery con