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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
The plates of a parallel plate capacitor are separated by a distance `d = 1 cm`. Two parallel sided dielectric slabs of thickness `0. 7cm` and `0.3cm` fill the space between the plates. If the dielectric constants of the two slabs are 3 and 5 respectively and a potential difference of `440V` is applied across the plates. Find (a) The electric field intensities in each of the slabs.(b) The ratio of electric energies stored in the first to that inthe second dielectric slab. |
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Answer» Correct Answer - (a) `5xx10^(4)V//m`, `3xx10^(4)V//m`; (b) `35//9` |
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| 52. |
A parallel plate capacitor is charged up to a potential of 300 volts. Area of the plates is `100 cm^(2)` and spacing between them is 2 cm. If the plates are moved apart to a distance of 2.5 cm without disconnected the power source, then `(in_(0)=9xx10^(-12)C^(2)N^(-1)m^(-2))`: (i) Electric field inside the capacitor when distance when distance is 2.5 cm :A. `15xx10^(2) V//m`B. `3xx10^(3) V//m`C. `12xx10^(3) V//m`D. `6xx10^(3) V//m` |
| Answer» Correct Answer - C | |
| 53. |
A parallel plate capacitor without any dielectric has capacitance `C_(0)`. A dielectric slab is made up of two dielectric slabs of dielectric constants K and 2K and is of same dimensions as that of capacitor plates and both the parts are of equal dimensions arranged serially as shown. If this dielectric slab is introduced (dielectric K enters first) in between the plates at constant speed, then variation of capacitance with time will be best represented by : A. B. C. D. |
| Answer» Correct Answer - B | |
| 54. |
A parallel plate capacitor is charged up to a potential of 300 volts. Area of the plates is `100 cm^(2)` and spacing between them is 2 cm. If the plates are moved apart to a distance of 2.5 cm without disconnected the power source, then `(in_(0)=9xx10^(-12)C^(2)N^(-1)m^(-2))`: (i) Electric field inside the capacitor when distance when distance is 2.5 cm :A. `303.75xx10^(-9) J`B. `-1215xx10^(-10)J`C. `5.06xx10^(-8)J`D. `303.75 xx 10^(-9)J` |
| Answer» Correct Answer - C | |
| 55. |
A parallel plate capacitor is charged up to a potential of 300 volts. Area of the plates is `100 cm^(2)` and spacing between them is 2 cm. If the plates are moved apart to a distance of 2.5 cm without disconnected the power source, then `(in_(0)=9xx10^(-12)C^(2)N^(-1)m^(-2))`: (i) Electric field inside the capacitor when distance when distance is 2.5 cm :A. `6xx10^(3) V//m`B. `3xx10^(3) V//m`C. `12xx10^(3) V//m`D. `15xx10^(3)V//m` |
| Answer» Correct Answer - D | |
| 56. |
Find capacitance of the capacitor shown in figure: in which four same sized dielectric slabs are inserted with their |
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Answer» Correct Answer - `(10k epsilon_(0)A)/(3d)` |
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| 57. |
A thin metal plate `P` is inserted between the plates of a parallel-plate capacitor of capacitance `C` in such a way that its edges touch the two plates (figure 31-Q2).The capacitance now becomes. |
| Answer» Correct Answer - D | |
| 58. |
Two capacitors `3muF` and `6muF` are connected in series across a potential difference of `120V`. Then the potential difference across `3muF` capacitor is:A. `40V`B. `60V`C. `80V`D. `100V` |
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Answer» Correct Answer - C |
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| 59. |
In the circuit shown in figure `C_(1)=5muF, C_(2)=29muC, C_(3)=6muF, C_(4)=3muF` and `C_(4)=7muF`. If in steady state potential difference between points `A` and `B` is 11 volt, calculate potential difference across `C_(3)`. |
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Answer» Correct Answer - `1.8V` |
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| 60. |
Find heaty produced on closing the switch `S` A. `0.0002J`B. `0.0005J`C. `0.00075`D. zero |
| Answer» Correct Answer - D | |
| 61. |
Four capacitors `C_(1)(=1 muF),C_(2)(=2muF),C_(3)(=3muF)` and `C_(4)(=4 muF)` are connected in a network as shown in the diagram. The emf of the battery is `E = 12 V` and its internal resistance is negligible. The keys `S_(1)` and `S_(2)` can be independetly put on or off. Indicate the charge on the capacitors by `q_(1),q_(2),q_(3)` and `q_(4)` respectively and the potential drops across them by `V_(1),V_(2),V_(3)` and `V_(4)` respectively. Initially key `S_(2)` is open. The key `S_(1)` is closed and teh capacitors are charged. If now key `S_(2)` be closed, the charge that will flow across this key is.A. `2.4 muC`B. `0.4 muC`C. `0.2 muC`D. `1.2 muC` |
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Answer» Correct Answer - A Before `S_(2)` is closed, `C_(1)` and `C_(3)` are in series and hence the total charge on their common plate is `(+Q-Q)=0`. Similarly for the plates joining `C_(2)` and `C_(4)`. However when `C_(2)` and `C_(4)` is closed, the charges read just to the values calculated in problem `86`. Hence total charge on the linking plates of `C_(1)` and `C_(3)` is `(-8.4 muC + 10.8 muC)=+ 2.4 muC` while the total charge on the linking plates of `C_(2)` and `C_(4)` is `(-16.8 muC + 14.4 muC = -2.4 muC` which shows that a charge of `2.4 muC` has crossed the key `S_(2)` from `(C_(2),C_(4))` to `(C_(1),C_(3))`. |
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| 62. |
Two capacitors `A` and `B` with capacities `3muF` and `2muF` are charged to a potential difference of `100 V` and `180V`, respectively. The plates of the capacitors are connected as show in figure with one wire of each capacitor free. The upper plate of `A` is positive and that of `B` is negastive. An uncharged `2muF` capcitor `C` with lead wires falls on the free ends to complete the circuit. Calculate a. the final charge on the three capacitors. b. the amount of electrostatic energy stored in the system before and after completion of the circuit. |
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Answer» Correct Answer - (a) `q_(1)=90 muC,q_(2)=210 muC,q_(3)=150muC` (b) `U_(f) =18 mJ,U_(i)=47.4 mJ`. (a) `Q_(1)=90muCmq_(2)=210 muC,q_(3)=150 muC` (b) `U_(f)=18 mJ`. |
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| 63. |
Four capacitors `C_(1)(=1 muF),C_(2)(=2muF),C_(3)(=3muF)` and `C_(4)(=4 muF)` are connected in a network as shown in the diagram. The emf of the battery is `E = 12 V` and its internal resistance is negligible. The keys `S_(1)` and `S_(2)` can be independetly put on or off. Indicate the charge on the capacitors by `q_(1),q_(2),q_(3)` and `q_(4)` respectively and the potential drops across them by `V_(1),V_(2),V_(3)` and `V_(4)` respectively. Initially key `S_(2)` is closed. Then the key `S_(1)` is now closed. Then the charges on the capacitors are.A. `q_(1)=q_(2)=24 muC,q_(3)= q_(4) = 12 mu C`B. `q_(1)=q_(2) =12 muC,q_(3)=q_(4) =24 muC`C. `q_(1)=10.8 muC,q_(2) = 14.4 muC, 3q_(3) =2q_(4),2q_(4) =25.2 muC`D. `2q_(1)=q_(2)=16.8 muC,4q_(3) =3q_(4) = 43.3 mu C` |
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Answer» Correct Answer - D If initially `S_(2)` is closed, `C_(1)` and `C_(2)` are in parallel, as also `C_(3)` and `C_(4)`. Effectively therefore `(C_(1)+C_(2))` and `(C_(2)+C_(4))` are in series when key `S_(1)` is closed. If `V` be the potential of the four common plates joined by `S_(2)`, when `S_(1)` is closed. Hence `q_(1)=(12-3.6)1=8.4 muC`, `q_(2)=(12-3.6)2 =16.8 muC` `q_(3)=(3.6)3=10.8 muC,q_(4)=(3.6)4=14.4 muC`. |
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| 64. |
Two capacitors of `2muF` and `3muF` are charged to `150 V` and `120 V`, respectively. The plates of capacitor are connected as shown in the figure. An uncharged capacitor of capacity `1.5muF` falls to the free end of the wire. Then A. Charge on the `1.5 mu F` capacitor will become `180 mu C` at steady state.B. Charge on the `2mu F` capacitor will become `120 mu C` at steady state.C. Positive charge flows through point A from left to right.D. Positive charge flows through point A from right to left . |
| Answer» Correct Answer - A::B::C | |
| 65. |
In the circuit shown in figure the switch S is closed at t = 0. A long time after closing the switch A. voltage drop across the capacitor is EB. current through the battery is `(E)/(R_(1)+R_(2)+R_(3))`C. energy stored in the capacitor is `(1)/(2)C (((R_(2)+R_(3))E)/(R_(1)+R_(2)+R_(3)))^(2)`D. current through the resistance `R_(4)` becomes zero |
| Answer» Correct Answer - B::C::D | |
| 66. |
In the adjoining diagram all the capacitors are initially uncharged, they are connected with a battery as a shown in figure. Then A. `Q_(1)=Q_(2)+Q_(3)` and `V=V_(1)+V_(2)`B. `Q_(1)=Q_(2)+Q_(3)` and `V=V_(1)+(V_(2)+V_(3))/(2)`C. `Q_(1)=Q_(2)+Q_(3)` and `V=V_(1)+V_(3)`D. `Q_(2)=Q_(3)` and `V=V_(2)+V_(3)` |
| Answer» Correct Answer - A::B::C | |
| 67. |
In the circuit shown in figure, the capacitors are initially uncharged. The current through resistor PQ just after closing the switch is A. 2A from P to QB. 2A from Q to PC. 6A from P to QD. zero |
| Answer» Correct Answer - D | |
| 68. |
Four capacitor and a battery of `emf 24 V` are connected as shown in the figure. Initially, `S` is open and the capacitors are uncharged. After `S` is closed and steady state is attained, the potential difference across the `4 mu f` capacitor is `7.5 V`. The capacitance in `mu f` of the capacitor `A` is. .A. 5B. 7C. 8D. 10 |
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Answer» Correct Answer - D P.d across the plates of `A=24-[7.5+(7.5 xx4)/(3)]=6.5 V` Charge on `A=(17.5 xx2)+(4xx7.5)=65 muc` `:.` Capacitance of `A=(65)/(6.5)=10 muf`. |
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| 69. |
Two unequal capacitors, initially uncharged, are connected in series across a battery. Which of the following is true.A. The potential across each is the sameB. The charge on each is the sameC. The energy stored in each is the sameD. The equivalent capacitance is the sum of the two capacitances |
| Answer» Correct Answer - B | |
| 70. |
Three initially uncharged capacitors are connected to a battery of 10V is parallel combination find out following (i) charge flow from the battery (ii) total energy stored in the capacitors (iii) heat produced in the circuit (iv) potential energy in the `3mu F` capacitor. |
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Answer» `(i) Q=(30+20+1)mu C=60 mu C` (ii) `U_("total")=(1)/(2)xx6xx10xx10=300mu J` `(iii) "heat produced"=60xx10-300=300mu J` (iv)`U_(3mu F)=(1)/(2)xx3xx10xx10=150 mu J` |
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| 71. |
Three capacitors of capacitances `3 muF, 9muF` and `18 muF` are connected one in series and another time in parallel. The ratio of equivalent capacitance in the two cases `((C_(s))/(C_(p)))` will beA. `1:15`B. `15:1`C. `1:1`D. `1:3` |
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Answer» Correct Answer - A |
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| 72. |
Two square metal plates of side `1 m` are kept `0.01 m` apart like a parallel plate capacitor in air in such a way that one of their edges is perpendicualr to an oil surface in the a tank filled with an insulating oil. The plates are connected to a battery of emf `55 V`. The plates are then lowered vertically into the oil at a speed of `0.001 ms^(-1)`. Calculate the current drawn from the battery during the process. (Dielectric constant of oil `=11, epsilon_(0) = 8.85 xx 10^(-12) N^(-1) m^(-2))`. |
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Answer» Correct Answer - `4.43 xx 10^(-9) A` `i=(dQ)/(dt) Q=CV,C=(epsilon_(0)A)/((x)/(K)+(d-x)) And v=(dx)/(dt)`. |
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| 73. |
A `2muF` capacitor is charged as shown in the figure. The percentage of its stored energy disispated after the switch S is turned to poistion 2 is |
| Answer» Correct Answer - D | |
| 74. |
Three capacitors each of capacity `4 muF` are to be connected in such a way that the effective capacitance is `6 muF`. This can be done byA. Connecting them in parallelB. connecting two in series and one in parallelC. connecting two in parallel and one in seriesD. connecting all of them in series |
| Answer» Correct Answer - B | |
| 75. |
Three capacitors each having capacitance `C=2 muF` are connected with a battery of emf`30 V` as shown in. when the switch S is closed, find a. the amount of charge flowing through the battery , b. the heat generated in the circuit, c. the energy supplied by the battery, d. the amount of charge flowing through the switch S. . |
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Answer» Correct Answer - (i) `20muC` (ii) `0.3ml` (iii) `0.6mJ` (iv) `60muC` |
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| 76. |
Consider the situation shown in figure. The plates of the capacitor have plate area `1A = lb1` and are clamped in the laboratory. The dielectric slab is released from rest with length a inside the capacitor. Neglecting any effect of friction or gravity, show that the slab will execute periodic motion and find its time period. |
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Answer» Correct Answer - `8xxsqrt((Md(l-a))/(bepsilon_(0)(K-1)V^(2)))` |
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| 77. |
Figure shows three circuits, each consisting of a switch and two capacitors, initially charged as indicated in the figure. In which circuit the charge on the left hand capacitor will change after the closing of the switch : A. 1B. 2C. 3D. All |
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Answer» Correct Answer - B::C |
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| 78. |
A radio capacitor of variable capacitance is made of `n` parallel plates each of area `A` and separated from each other by a distanced. The alternate plates are connected together. The capacitance of the combination is.A. `(n A in_(o))/(d)`B. `((n-1) A in_(o))/(d)`C. `((2n -1)A in_(o))/(d)`D. `((n-2)A in_(o))/(d)` |
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Answer» Correct Answer - B Due to `n` plates `n-1` capacitors are formed. |
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| 79. |
When two capacitors are joined in series the resultance capacity is `2.4 muF` and when the same two are joined in parallel the resultant capacity is `10 mu F`. Their individual capacities are.A. `7 mu F,3 mu F`B. `1 mu F,9 mu F`C. `6 mu F,4 mu F`D. `8 mu F,2 mu F` |
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Answer» Correct Answer - C `C_(S)=(C_(1)C_(2))/(C_(1)+C_(2)) ,C_(1)+C_(2)=C_(P)`. |
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| 80. |
The graph given below shows the variation of electric field `E` (in `MV//m`) with time `t` (in `mus`) in a parallel plate capacitor Consider the statements: (1) The displacement current through a `1m^(2)` region perpendicular to the during the time interval `t=0` to `t=4mus` is `0.0885A` (given `epsilon_(0)=8.85xx10^(-12)` SI unit) (2) The displacement current through `1m^(2)` region perpendicular to the field during the time interval `t=4mus` to `8mus` is zero. Which of the statements given above is/are correct:A. 1 onlyB. 2 onlyC. both 1 and 2D. neither 1 nor 2 |
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Answer» Correct Answer - C |
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| 81. |
Equipotential surfacesA. are closer in regions of large electric fields compared to regions of lower electric fieldsB. will be more crowded near sharp edges of a conductor.C. will be more crowded near regions of large charge densitiesD. will aways be equally spaced |
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Answer» Correct Answer - A::B::C `E=-(dV)/(dr) or dr=-(dV)/(E)` For a fixed value of `dV, dr prop - (1)/( E)` , which implies that spacing between two equipotential surfaces decreases as `E` increases. So, equipotential surfaces are closer in regions of large electric fields. At sharp deges `a=of` conductor, charge density is more. So, electric field is large and hence the equipotential surfaces will be more crowded. |
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| 82. |
Select the correct statements (s).A. Capacitance of a capacitor depends on the charge on it.B. Capacitance of a capacitor does not depend on the charge on it.C. Capacitance of a capacitor does not depend on the potential differenceD. Capacitance of a capacitor does not depend on the material with which the capacitor plates are prepared. |
| Answer» Correct Answer - B::C::D | |
| 83. |
In the given circuit, `K_(1)` and `K_(2)` are open initially and the capacotors are uncharged, After `K_(1)` and `K_(2)` are closed and steady state is attained. Now answer the following questions. The charge on `5 mu c` capacitor is :A. `8 mu c`B. `35 mu c`C. `6 mu c`D. zero |
| Answer» Correct Answer - B | |
| 84. |
In the given circuit, `K_(1)` and `K_(2)` are open initially and the capacotors are uncharged, After `K_(1)` and `K_(2)` are closed and steady state is attained. Now answer the following questions. The charge on `4 mu F` capacitor is :A. `8 mu c`B. `35 mu c`C. `6 mu c`D. zero |
| Answer» Correct Answer - A | |
| 85. |
In the given circuit, `K_(1)` and `K_(2)` are open initially and the capacotors are uncharged, After `K_(1)` and `K_(2)` are closed and steady state is attained. Now answer the following questions. The charge in `3 mu F` capacitor is :A. `8 mu c`B. `35 mu c`C. `27 mu c`D. zero |
| Answer» Correct Answer - C | |
| 86. |
In the given circuit, `K_(1)` and `K_(2)` are open initially and the capacotors are uncharged, After `K_(1)` and `K_(2)` are closed and steady state is attained. Now answer the following questions. The charge on `6 mu F` capacitor is :A. `8 mu c`B. `35 mu c`C. `6 mu c`D. zero |
| Answer» Correct Answer - D | |
| 87. |
A parallel plate capacitor is located horizontally, so that one of its plates is submerged into liquid while the other is over the surface. The dielectric constant of the liquid is equal to `k`. Its density is equal to `rho`. To what height will the level of the liquid in the capacitor rise after its plates gets a charge of surface density `sigma` ? .A. `h=((k^2-1)sigma^(2))/(2 epsilon_(0) k^2 rho g)`B. `h=((k-1)sigma^(2))/(epsilon_(0) k rho g)`C. `h=(2(k-1)sigma^(2))/(epsilon_(0) k rho g)`D. `h=0` |
| Answer» Correct Answer - A | |
| 88. |
A capacitor of capacitance C is charged to a potential difference V from a cell and then disconnected from it. A charge +Q is now given to its positive plate. The potential difference across the capacitor is nowA. VB. `V + (Q)/( C)`C. `V + (Q)/(2 C)`D. `V -(Q)/( C)`, if `V lt CV` |
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Answer» Correct Answer - C `E=(sigma)/(in_(0))=((Q)/(2)+CV)/(A in_(0)),V=Ed=((Q)/(2)+CV)/((A in_(0))/(d))` `= ((Q)/(2)+CV)/(C)=V+(Q)/(2C)`. |
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| 89. |
The equivalent capacitance between `X` and `Y` is `A. `5//6muF`B. `7//6muF`C. `8//3muF`D. `1muF` |
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Answer» Correct Answer - C |
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| 90. |
Four capacitors are connected as shown in figuere to a `30 V` battery. The potential difference between points `a` and `b` A. `5V`B. `9V`C. `10V`D. `13V` |
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Answer» Correct Answer - D |
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| 91. |
A dielectric slab fills the space between the square plates of a parallel-plate capacitor. The side of each plate of the capacitor is `L`. The magnitude of the bound charges on the slab is `75%` of the magnitude of the free charge on the plates. The capacitance is `480muF` and the maximum charge that can be stored on the capacitor is `240epsilon_(0)L^(2)E_("max"),` where `E_("max")` is the breakdown strength of the medium:A. The dielectric constant for the dielectric slab is 4B. Without the dielectric, the capacitance of the capacitor would be `360muF`C. The plate area is `60L^(2)`D. If the dielectric slab is having the same area as that of the capacitor plate but the width is half the separation between plates of capacitor, the capacitance would be `192muF` |
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Answer» Correct Answer - A::C::D |
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| 92. |
The terminals of a battery of emf V are connected to the two plates of a parallel plate capacitor. If the space between the plates of the capacitor is filled with an insulator of dielectric constant K, then :A. the electric field in the space between the plates does not changeB. the capacitance of the capacitor increasesC. the charge stored in the capacitor increasesD. the electrostatic energy stored in the capacitor decreases |
| Answer» Correct Answer - A::B::C | |
| 93. |
Select correct statement for a capacitor having capacitance `C`, is connected to a source of constant `emf E`A. Almost whole of the energy supplied by the battery will be stored in the capacity, if resistance of connecting wire is negligibly smallB. Energy received by the capacitor will be half of energy supplied by the battery only when the capacitor was initially uncharged.C. Stored energy in the capacitor must increases even it the capacitor had an initial chargeD. Energy stored depends on type of the source of `emf`. |
| Answer» Correct Answer - C | |
| 94. |
Van Graff genetor is used to :A. supply electricity for industrial useB. produce intense magnetic fieldsC. generate high voltageD. obtain highly penetrating X-rays. |
| Answer» Correct Answer - C | |
| 95. |
Three charged particles are initially in position `1`, "They are free to move and they come in position" `2` "after some time. Let" `U_(1)` and `U_(2)` be the electrostatic potential energies in position `1 and 2`. ThenA. `U_(1) gt U_(2)`B. `U_(2) gt U_(1)`C. `U_(1) = U_(2)`D. `U_(2) ge U_(1)` |
| Answer» Correct Answer - A | |
| 96. |
A number of spherical conductors of different radii have same potential. Then the surface charge density on them.A. is proportional to their radiiB. is inversely proportional to their radiiC. are equalD. is proportional to square of their radii |
| Answer» Correct Answer - B | |
| 97. |
In the circuit shown in figure, charge on `10 muF` capacitor is given as A. `2xx10^(-3)C`B. `16xx10^(-4)C`C. `4xx10^(-3)C`D. `8xx10^(-4)C` |
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Answer» Correct Answer - A |
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| 98. |
The distance between the plates of a charged parallel plate copacitor is `5cm` and electric field inside the plates is `200V cm^(-1)`. An uncharged metal bar of width `2 cm` is fully immersed into the capacitor. The length of the metal bar is same as that of plate of capacitor. The voltage across capacitor after the immersion of the bar is-A. zeroB. `400 V`C. `600 V`D. `100 V` |
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Answer» Correct Answer - C `V = E (d-t) = 20 xx (5-2) = 600V` |
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| 99. |
A parallel plate capacitor is charged and then isolated. On increasing the plate separationA. decreases constant decreasesB. increases increases increasesC. constant decreases decreasesD. constant increases increases |
| Answer» Correct Answer - D | |
| 100. |
The equivalent capacitance of the arrangement shown in figure, if `A` is the area of each plate is A. `(a in_(0))/(d)[(K_(1))/(2)+(K_(2)K_(3))/(K_(2)+K_(3))]`B. `(a in_(0))/(2d)[(K_(2))/(2)+(K_(1)K_(3))/(K_(1)+K_(3))]`C. `(a in_(0))/(3d)[(K_(3))/(2)+(K_(1)K_(2))/(K_(1)+K_(2))]`D. `(a in_(0))/(d)[(K_(1))/(2)+(K_(1)+K_(2))/(K_(2)K_(3))]` |
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Answer» Correct Answer - A `(K_(1) in_(o)((A)/(2)))/(d),C_(2)=(K_(2)in_(o)A)/(d),C_(3)=(K_(3) in_(o)A)/(d)` `:. C=(C_(2)C_(3))/(C_(2)+C_(3))+C_(1)`. |
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