JEE Questions for Physics Electrostatics I Quiz 22 - MCQExams.com

A capacitor is charged by using a battery which is then disconnected. A dielectric slab is then slipped between the plates, which result in
  • Reduction of charge on the plates and increase of potential difference across the plates
  • Increase in the potential difference across the plate, reduction in the stored energy, but no change in the charge on the plates
  • Decrease in the potential difference across the plates, reduction in the stored energy, but no change in the charge on the plates
  • None of the above
The earth has Volume \'V\' and Surface Area \'A\' then capacitance would be

  • Physics-Electrostatics I-72403.png
  • 2)
    Physics-Electrostatics I-72404.png

  • Physics-Electrostatics I-72405.png

  • Physics-Electrostatics I-72406.png
Two conducting spheres of radii R1 and R2having charges Q1 and Q2respectively are connected to eachother. There is
  • No change in the energy of the system
  • An increase in the energy of the system
  • Always a decrease in the energy of the system
  • A decrease in the energy of the system unless Q1R2 = C2R1
A series combination of n1 capacitors each of value C1, is charged by a source of potential difference 4V. When C2, is charged by a source of potential difference V, it has the same (total) energy stored in it, as the first combination has, The value of C2, in terms of C1, is then

  • Physics-Electrostatics I-72409.png
  • 2)
    Physics-Electrostatics I-72410.png

  • Physics-Electrostatics I-72411.png

  • Physics-Electrostatics I-72412.png
The energy stored in a condenser of capacity C which has been raised to a potential V is given by

  • Physics-Electrostatics I-72414.png
  • 2)
    Physics-Electrostatics I-72415.png
  • CV

  • Physics-Electrostatics I-72416.png
Capacitors are used in electrical circuits where appliances need more
  • Current
  • Voltage
  • Watt
  • Resistance
Eight drops of mercury of equal radii possessing equal charges combine to form a big drop. Then the capacitance of bigger drop compared to each individual small drop is
  • 8 times
  • 4 times
  • 2 times
  • 32 times
Separation between the plates of a parallel plate capacitor is d and the area of each plate is A. When a slab of material of dielectric constant k and thickness t(t

  • Physics-Electrostatics I-72420.png
  • 2)
    Physics-Electrostatics I-72421.png

  • Physics-Electrostatics I-72422.png

  • Physics-Electrostatics I-72423.png
The capacity of parallel plate condenser depends on
  • The type of metal used
  • The thickness of plates
  • The potential applied across the plates
  • The separation between the plates
The energy required to charge a parallel plate condenser of plate separation d and plate area of cross-section A such that the uniform electric fieldbetween the plates is E, is

  • Physics-Electrostatics I-72426.png
  • 2)
    Physics-Electrostatics I-72427.png

  • Physics-Electrostatics I-72428.png

  • Physics-Electrostatics I-72429.png
Eight small drops, each of radius r and having same charge q are combined to form a big drop. The ratio between the potentials of the bigger drop and the smaller drop is
  • 8 : 1
  • 4 : 1
  • 2 : 1
  • 1 : 8
The capacitance of a spherical condenser is 1 µF. If the spacing between the two spheres is 1 mm then the radius of the outer sphere is
  • 30 cm
  • 6 m
  • 5 cm
  • 3 m
When air in a capacitor is replaced by a medium of dielectric constant K, the capacity
  • Decreases K times
  • Increases K times
  • Increases K2 times
  • Remains constant
64 drops each having the capacity C and potential V are combined to form a big drop. If the charge on the smalldrop is q, then the charge on the big drop will be
  • 2q
  • 4q
  • 16q
  • 64q
The capacity of a spherical conductor in MKS system is

  • Physics-Electrostatics I-72436.png
  • 2)
    Physics-Electrostatics I-72437.png

  • Physics-Electrostatics I-72438.png

  • Physics-Electrostatics I-72439.png
The capacitance C of a capacitor is
  • Independent of the charge and potential of the capacitor
  • Dependent on the charge and independent of potential
  • Independent of the geometrical configuration of the capacitor
  • Independent of the dielectric medium between the two conducting surfaces of the capacitor
The respective radii of the two spheres of a spherical condenser are 12 cm and 9 cm The dielectric constant of the medium between them is 6. The capacity of the condenser will be
  • 240 pF
  • 240
  • 240 F
  • None of these
Consider a parallel plate capacitor with plates 20 cm by 20 cm and separated by 2mm. The dielectric constant of the material between the plates is 5. The plates are connected to a voltage sources of 500 V. The energy density of the field between the plates will be close to
  • 2.65 J/m3
  • 1.95 J/m3
  • 1.38 J/m3
  • 0.69 J/m3
A condenser of capacity C is charged to a potential difference of V1. The plates of the condenser are then connected to an ideal inductor of inductance L. The current through the inductor when the potential difference across the condenser reduces to V2 is

  • Physics-Electrostatics I-72443.png
  • 2)
    Physics-Electrostatics I-72444.png

  • Physics-Electrostatics I-72445.png

  • Physics-Electrostatics I-72446.png
There is an air filled 1pF parallel plate capacitor. When the plate separation is doubled and the space is filled with wax, the capacitance increase to 2pF The dielectric constant of wax is
  • 2
  • 4
  • 6
  • 8
N identical spherical drops charged to the same potential V are combined to form a big drop. The potential of the new drop will be
  • V
  • V/N
  • V × N
  • V × N2/3
The plates of parallel plate capacitor are charged upto 100V. A 2mm thick plate is inserted between the plates. Then to maintain the same potential difference, the distance between the plates is increased by 1.6 mm. The dielectric constant of the plate is
  • 5
  • 1.25
  • 4
  • 2.5
Force acting upon a charged particle kept between the plates of a charged condenser is F. It one plate of the condenser is removed, then the force acting on the same particle will become
  • 0
  • F/2
  • F
  • 2F
A frictionless dielectric plate S is kept on a frictionless table T. A charged parallel plate capacitance C (of which the plates are frictionless) at kept near it. Theplate S is in between the plates. When the plate S is left between the plates
Physics-Electrostatics I-72467.png
  • It will remain stationary on the table
  • It is pulled by the capacitor and will pass on the other end
  • It is pulled between the plates and will remain there
  • All the above statements are false
Pick out the false statement from the following
  • The direction of eddy current is given by Fleming's right hand rule
  • A choke coil is a pure inductor used for controlling current in an a.c circuit

  • Physics-Electrostatics I-72468.png

  • Physics-Electrostatics I-72469.png
  • Induction coil is a powerful equipment used for generating high voltages
The distance between the circular plates of a parallel plate condenser 40 mm in diameter, in order to have same capacity as a sphere of radius 1 m is
  • 0.01 mm
  • 0.1 mm
  • 1.0 mm
  • 10 mm
The capacitance of a metallic sphere will be if its radius is nearly
  • 9 km
  • 10 m
  • 1.11 m
  • 1.11 cm
Energy stored in capacitor and dissipated during charging a capacitor bear a ratio
  • 1 : 1
  • 1 : 2
  • 1 : 1/2
  • 2 : 1
The distance between the plates of a parallel plate capacitor is d. A metal plate of thickness d / 2 is placed between the plates. The capacitance would then be
  • Unchanged
  • Halved
  • Zero
  • Doubled
The capacitance of an air capacitor is 15µF the separation between the parallel plates is 6 mm. A copper plate of 3 mm thickness is introduced symmetrically between the plates. The capacitance now becomes
  • 5µF
  • 7.5µF
  • 22.5µF
  • 30µF
A light bulb, a capacitor and a battery are connected together as shown here, with switch S initially open, When the switch S is closed, which one of the following is true?
Physics-Electrostatics I-72479.png
  • The bulb will light up for an instant when the capacitor starts charging
  • The bulb will light up when the capacitor is fully charged
  • The bulb will not light up at all
  • The bulb will light up and go off at regular intervals
The potentials of the two plates of capacitor are +10 V and –10 V. The charge on one of the plates is 40C. Thecapacitance of the capacitor is
  • 2F
  • 4 F
  • 0.5 F
  • 0.25 F
The diameter of each plate of an air capacitor is 4 cm. To make the capacity of thisplate capacitor equal to that of 20 cm diameter sphere, the distance between the plates will be
  • 4 × 10–3 m
  • 1 × 10–3 m
  • 1 cm
  • 1 × 10–3 cm
A spherical condenser has inner and outer spheres of radii a andb respectively. The space between the two is filled with air. The difference between the capacities of two condensers formed when outer sphere is earthed and when inner sphere is earthed will be
  • Zero
  • 2)
    Physics-Electrostatics I-72482.png

  • Physics-Electrostatics I-72483.png

  • Physics-Electrostatics I-72484.png
The expression for the capacity of the capacitor formed by compound dielectric placed between the plates of a parallel plate capacitor as shown in figure, will be (area of plate = A)
Physics-Electrostatics I-72486.png

  • Physics-Electrostatics I-72487.png
  • 2)
    Physics-Electrostatics I-72488.png

  • Physics-Electrostatics I-72489.png

  • Physics-Electrostatics I-72490.png
An insulator plate is passed between the plates of a capacitor. Then the displacement current
Physics-Electrostatics I-72496.png
  • First flows from A to B and then from B to A
  • First flows from B to A then from A to B
  • Always flows from B to A
  • Always flows from A to B
A charge of 10–9C is placed on each of the 64 identical drops of radius 2 cm They are then combined to form a bigger drop. Find its potential
  • 7.2 × 103 V
  • 7.2 × 102V
  • –1.44 × 102V
  • 1.44 × 103V
The plates of a parallel plate capacitor of capacity 50µC are charged to a potential of 100 volts and then separated from each other so that the distance between them is doubled. How much is the energy spent in doing so?
  • 25 × 10–2J
  • –12.5 × 10–2 J
  • –25 × 10–2 J
  • 12.5 × 10–2 J
The area of the plates of a parallel plate condenser is A and the distance between the plates is 10 mm. There are two dielectric sheets in it, one of dielectric constant 10 and thickness 6 mm and the other of dielectric constant 5 and thickness 4 mm The capacity of the condenser is

  • Physics-Electrostatics I-72503.png
  • 2)
    Physics-Electrostatics I-72504.png

  • Physics-Electrostatics I-72505.png

  • Physics-Electrostatics I-72506.png
A parallel plate consider with oil between the plates (dielectric constant of oil K =has a capacitance C. If the oil is removed, then capacitance of the capacitor becomes

  • Physics-Electrostatics I-72517.png
  • 2C

  • Physics-Electrostatics I-72518.png

  • Physics-Electrostatics I-72519.png
The energy stored in the condenser is

  • Physics-Electrostatics I-72523.png
  • 2)
    Physics-Electrostatics I-72524.png

  • Physics-Electrostatics I-72525.png

  • Physics-Electrostatics I-72526.png
A battery is used to charge a parallel plate capacitor till the potential difference between the plates becomes equal to the electromotive force of the battery. The ratio of the energy stored in the capacitor and the work done by the battery will be
  • 1
  • 2
  • 1/4
  • 1/2
Two identical charged spherical drops each of capacitance C merge to form a single drop. The resultant capacitance is
  • Equal to 2C
  • Greater than 2C
  • Less than 2C but greater than C
  • Less than C
The capacitance of a parallel plates capacitor with air as medium is 3µF. With the introduction of a dielectric medium between the plates, the capacitance becomes 15µF. The permittivity of medium is
  • 5
  • 15
  • 0.44 × 10–10C2N–1m–2
  • 8.854 × 10–11C2N–1m–2
The radius of a metallic sphere if its capacitance is1/9F, is
  • 106m
  • 107m
  • 109m
  • 108m
The ratio of charge to potential of a body is known as
  • Capacitance
  • Conductance
  • Inductance
  • Resistance
If the capacity of a spherical conductor is 1 pico farad then its diameter would be
  • 1.8 × 10–3 m
  • 18 × 10–3 m
  • 1.8 × 10–5 m
  • 18 × 10–7 m
A parallel plate air capacitor is capacitor to a potential difference of V. After disconnecting the battery, distance between the plates of the capacitor is increased using an insulating handle. As a result, the potential difference between the plates
  • Decreases
  • Increases
  • Become zero
  • Does not change
A 10pF capacitor is connected to a 50 V battery. How much electrostatic energy is stored in the capacitor?
  • 1.25 × 10–8 J
  • 2.5 × 10–7 J
  • 3.5 × 10–5 J
  • 4.5 × 10–2J
Three capacitors each of capacitance C and of breakdown voltage V are joined in senes. The capacitance and breakdown voltage of the combination will be

  • Physics-Electrostatics I-72586.png
  • 2)
    Physics-Electrostatics I-72587.png

  • Physics-Electrostatics I-72588.png

  • Physics-Electrostatics I-72589.png
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