.1 A hemisphere of radius R is charged uniformly with surface charge density s. What will be the potential at the center?
[a] sR/e0 [b] s/4e0
[c] s/2e0 [d]4sR/3e0
Q.2 A particle having charge a and mass m is projected in uniform electric filed E with u making an angle q. Then
[a] if gravitational field is present path may be straight line
[b] if gravitational field is absent path may be a straight line
[c] if gravitational field is absent path may be parabola
[d]if gravitational field is absent path may be a straight line
Q.3 In Milikan’s oil drop experiment, an oil drop carrying charge Q is held stationary by a potential difference f 2400V between plates. To keep the drop of half the radius stationary, the potential difference has to be made 600V. what is the charge on the second drop?
[a] Q/4 [b] Q/2
[c] Q [d] 3Q/2
Q.4 Two condensers C1 and C2 are joined as shown in figure. The potential of A is V1 and that of B is V2. The potential of D will be
[a] 
[b]
[b]
[c]
[d] 
[d]
Q.5 A large metal sheet has surface charge density s. An electron of mass m and charge e leaves the surface at some point A with speed u and returns to it another point B. Neglecting the acceleration due to gravity find the maximum value of distance AB.
[a] u2me0/se [b]u2ee0/ms
[c]u2e/e0sm [d]u2se/e0m
Q.6 Two square metallic plates of side a=1m are kept d=8.85mm apart like in parallel plate capacitor, in such a way that surfaces are normal to the oil surface in tank with insulating oil [K=10]. The plates are connected to battery of emf 500V as shown in figure. The plates are lowered vertically into oil at speed of 103ms. Neglecting resistance of connecting wires, calculate the current drawn from the battery during the process
[a] 5x10-19A [b] 0.5x10-9A
[c] 5 x 10-9A [d] 50 x 10-9A
Q.7 A hollow metal sphere of radius 5cm is charged such that the potential on its surface is 10V. the potential at the center of sphere is
[a] zero [b] 10V
[c] same as at a point 5cm from surface
[d] same as at a point 25cm from surface
Q.8 Three charges Q, +q and +q are placed at the vertices of right angles isosceles triangle as shown. The net electrostatic energy of the configuration is zero if Q equal to
[a] 
[b]
[b]
[c] –2q [d] +q
Q.9 For the circuit shown in figure, which of the following statements is true?
[a] with S1 closed V1=15V, V2=20V 
[b] with S3 closed V1=V2=25V
[c] with S1 and S2 closed V1=V2=0
[d] with S1 and S3 closed V1=30V and V2=20V
Q.10 A parallel plate 0.1MW resistor and 10mF capacitor is connected across a 1.5V source of negligible resistance. The time required for the capacitor to charge upto 0.75V is approximately
[a] infinite [b] loge2
[c] log102 [d] zero
Q.11 Two point charges +q and –q are held fixed at [-d,0] and [d,0] respectively of x-y coordinate system. Then
[a] the electric field at all points on the x axis has the same direction.
[b] work has to be done to bring test charge from infinity to origin
[c] electric field at all points on y axis is along x axis
[d] the dipole moment is 2qd along x axis
Q.12 A parallel plate capacitor of capacitance C is connected to battery and is charged to potential difference V. another capacitor of capacitance 2C is similarly charged to pd 2V. The charging battery is now disconnected and the capacitors are connected in parallel to each other in such a way that the positive terminal of one is connected to the negative terminal of the other. The final energy of the configuration is
[a] zero [b] 3CV2/2
[c] 25CV2/6 [d] 9CV2/2
Q.13 Two equal point charge are at x=a and x=-a on the x-axis. Another charge Q is placed at the origin. The change in electrical potential energy of Q, when it is displaced by a small distance x along the x-axis, is approximately proportional to
[a] x [b] x2
[c]x3 [d]1/x
Q.14 A uniform electric field pointing in the positive x direction exists in a region. Let A be the origin, B be the point on the x axis at x=+1cm and C be the point on the yaxis y=+1cm. Then the potential of point A,B and C satisfy
[a] Va < Vb [b] Va>Vb
[c]Va< Vc [d]Va>Vc
Q.15 A parallel plate capacitor is charged and the charging battery is disconnected. If the plates of the capacitor are moved further apart by means of insulating handles
[a] the charge on the capacitor increases
[b] the voltage across the plates increases
[c] capacitance increases
[d] electrostatic energy stored in the capacitor decreases
Q.16 A cubical block of mass m containing a net positive charge Q is placed on a smooth horizontal surface which terminates in a vertical wall. the distance between the wall and the block is d. a horizontal electric field E directed towards the wall is suddenly switched on. Assuming elastic collision [if any], the time period of the resulting oscillation is
[a]
[b] 
[b]
[c] 
[d] 
[d]
Q.17 A particle of mass m and charge q is placed at rest in uniform electric field E as shown and released. The kinetic energy it attains after moving distance y is
[a]qEy/2 [b]qE2y
[c]qEy [d]mqEy/2
Q.18 A semicircular ring of radius 0.5m is uniformly charged with the total charge of 1.4x10-9C. The electric field intensity at the center of this ring is
[a] 100V/m [b]320V/m
[c] 64V/m [d]32V/m
Q.19 Three identical metallic uncharged spheres A,B and C of radius a are kept on the corners of an equilateral triangle of side d[d>>a] . A fourth sphere of radius a which has charge Q touches A and is then removed to position far away. B is earthed and then the earth connection is removed. C is then earthed. The charge on C is
[a]
[b] 
[b]
[c] 
[d] 
[d]
Q.20 A non conducting massless rod of length 10cm carries two small metallic balls of mass 5gm each. There is charge of 1μC on each ball, fixed at each end of the rod. The rod is held in an electric field of 50V/m, making small angle θ with the field. When the rod is released, it executes SHM. Its time period is
[a]2.8s [b]0.14s
[c]14s [d]1.4s
Q.21 A solid conducting sphere has charge Q surrounded by an uncharged concentric hollow spherical shell. Let the potential difference between the surface of the solid sphere and that of the outer surface of the spherical shell be V. if the shell is now given a charge -3Q the new potential difference between the same surface is
[a]V [b]2V
[c] 4V [d]-2V
Q.22 two identically charged spheres are suspended by strings of equal length. The strings makes an angle of 300 with each other. When suspended in a liquid of density 0.8gm/cc the angle remains the same. If the density of the sphere is 1.6gm/cc then the dielectric constant of the liquid is
[a]2 [b]3.5
[c] 8 [d]4
Q.23 27 drops of mercury are charged simultaneously to the same potential of 10V. all these drops combines to form a big drop. If the drops are assumed to be spherical, the potential of the large drop is
[a]90V [b]270V
[c]135V [d]10V
Q.24 Three charges each of value q are placed at the corners of an equilateral triangle. A fourth charge Q is placed at the center of the triangle. If Q=-q,
[a]the charges will move towards the center
[b]the charges will move away from center
[c]the charges will be stationary
[d] the charges will move in any direction
Q.25 What is the electric potential at the center of hemisphere having radius R and surface charge density σ:
[a]σ/2ε [b]σ/ε
[c]σR/ε [d]σR/2ε
Q.26 A parallel plate capacitor is first connected to DC source. It is then disconnected and immersed in a liquid dielectric. Then
[a]its capacity increases [b]its capacity decreases
[c]the liquid level between the plates increases
[d]none of these
Q.27 The capacitance of two oppositely charged metal spheres of same radius when far apart will be equal to
[a]2C [b]C/2
[c]C/4 [d]4C
Q.28 A small metal ball is suspended in a uniform electric field with the help of an insulated thread. If the high energy X-ray beam falls on it
[a]the ball will be directed in the direction of the field
[b]deflected opposite to the field direction
[c]perpendicular to the direction of the field
[d]the ball will not deflect at all
Q.29 The electric field strength at a distance r from the center of charged sphere of radius R is E. if r>R, how much work will be done in bringing a test charge q0 from infinity to that point?
[a] q0RE [b]q0RE/2
[c]q0rE [d]q0rE/2
Q.30 Two metal spheres of radii a and b are connected by a thin wire. Their separation is very large compared with their dimensions. A charge Q is introduced into this system. The capacitance of the system is
[a] 4πε[ab] [b]2πε[a+b]
[c]4πε[a+b] [d]none of these
Q.31 A capacitor of capacity 5μF is charged to a potential difference of 100V. The battery is disconnected and then connected in parallel to an uncharged capacitor of capacitance C. the potential difference measured across this combination is 25V. the capacitance is
[a]15μF [b]10μF
[c]5μF [d]20μF
Q.32 In the above problem, the ratio of energy U0 in the capacitor of 5μF and U when it is connected in parallel to an uncharged capacitor of capacitance C is given by
[a] 4/3 [b]4/5
[c] 5/2 [d]4/1
Q.33 Two parallel plate capacitors of capacitance C and 2C are connected in parallel and charged to potential difference of V volt. The battery is then disconnected and the region between the plates is filled with a material of dielectric constant k. the potential difference across the capacitors now becomes
[a]2V/K [b]3V/K
[c]3V/[K+2] [d]2V/[K+3]
Q.34 A parallel plate capacitor is charged and then the charging battery is disconnected. If the plates are moved farther apart by means of insulating handles
[a] the charge on the capacitor increases
[b] the voltage across the plates increases
[c]the capacitance increases
[d] the electrostatic energy stored in the capacitor increases
Q.35 A parallel plate capacitor has plate area A and separation d and is charged to potential difference V0. the charging battery is disconnected and the plates are pulled apart to 3 times the initial separation. The work required to separate the plates is
[a] 
[b] 
[b]
[c] 
[d] 
[d]
Q.1 A cubical block of mass m containing a net positive charge Q is placed on a smooth horizontal surface which terminates in a vertical wall. the distance between the wall and the block is d. a horizontal electric field E directed towards the wall is suddenly switched on. Assuming elastic collision [if any], the time period of the resulting oscillation is
[a] [b]
[b]
[c] [d]
[d]
Q.2 A particle of mass m and charge q is placed at rest in uniform electric field E as shown and released. The kinetic energy it attains after moving distance y is
[a]qEy/2 [b]qE2y
[c]qEy [d]mqEy/2
Q.3 A semicircular ring of radius 0.5m is uniformly charged with the total charge of 1.4x10-9C. The electric field intensity at the center of this ring is
[a] 100V/m [b]320V/m
[c] 64V/m [d]32V/m
Q.4 Three identical metallic uncharged spheres A,B and C of radius a are kept on the corners of an equilateral triangle of side d[d>>a] . A fourth sphere of radius a which has charge Q touches A and is then removed to position far away. B is earthed and then the earth connection is removed. C is then earthed. The charge on C is
[a] [b]
[b]
[c] [d]
[d]
Q.5 A non conducting massless rod of length 10cm carries two small metallic balls of mass 5gm each. There is charge of 1μC on each ball, fixed at each end of the rod. The rod is held in an electric field of 50V/m, making small angle θ with the field. When the rod is released, it executes SHM. Its time period is
[a]2.8s [b]0.14s
[c]14s [d]1.4s
Q.6 A solid conducting sphere has charge Q surrounded by an uncharged concentric hollow spherical shell. Let the potential difference between the surface of the solid sphere and that of the outer surface of the spherical shell be V. if the shell is now given a charge -3Q the new potential difference between the same surface is
[a]V [b]2V
[c] 4V [d]-2V
Q.7 two identically charged spheres are suspended by strings of equal length. The strings makes an angle of 300 with each other. When suspended in a liquid of density 0.8gm/cc the angle remains the same. If the density of the sphere is 1.6gm/cc then the dielectric constant of the liquid is
[a]2 [b]3.5
[c] 8 [d]4
Q.8 27 drops of mercury are charged simultaneously to the same potential of 10V. all these drops combines to form a big drop. If the drops are assumed to be spherical, the potential of the large drop is
[a]90V [b]270V
[c]135V [d]10V
Q.9 Three charges each of value q are placed at the corners of an equilateral triangle. A fourth charge Q is placed at the center of the triangle. If Q=-q,
[a]the charges will move towards the center
[b]the charges will move away from center
[c]the charges will be stationary
[d] the charges will move in any direction
Q.10 What is the electric potential at the center of hemisphere having radius R and surface charge density σ:
[a]σ/2ε [b]σ/ε
[c]σR/ε [d]σR/2ε
Q.11 A parallel plate capacitor is first connected to DC source. It is then disconnected and immersed in a liquid dielectric. Then
[a]its capacity increases [b]its capacity decreases
[c]the liquid level between the plates increases
[d]none of these
Q.12 The capacitance of two oppositely charged metal spheres of same radius when far apart will be equal to
[a]2C [b]C/2
[c]C/4 [d]4C
Q.13 A small metal ball is suspended in a uniform electric field with the help of an insulated thread. If the high energy X-ray beam falls on it
[a]the ball will be directed in the direction of the field
[b]deflected opposite to the field direction
[c]perpendicular to the direction of the field
[d]the ball will not deflect at all
Q.14 The electric field strength at a distance r from the center of charged sphere of radius R is E. if r>R, how much work will be done in bringing a test charge q0 from infinity to that point?
[a] q0RE [b]q0RE/2
[c]q0rE [d]q0rE/2
Q.15 Two metal spheres of radii a and b are connected by a thin wire. Their separation is very large compared with their dimensions. A charge Q is introduced into this system. The capacitance of the system is
[a] 4πε[ab] [b]2πε[a+b]
[c]4πε[a+b] [d]none of these
Q.16 A capacitor of capacity 5μF is charged to a potential difference of 100V. The battery is disconnected and then connected in parallel to an uncharged capacitor of capacitance C. the potential difference measured across this combination is 25V. the capacitance is
[a]15μF [b]10μF
[c]5μF [d]20μF
Q.17 In the above problem, the ratio of energy U0 in the capacitor of 5μF and U when it is connected in parallel to an uncharged capacitor of capacitance C is given by
[a] 4/3 [b]4/5
[c] 5/2 [d]4/1
Q.18 Two parallel plate capacitors of capacitance C and 2C are connected in parallel and charged to potential difference of V volt. The battery is then disconnected and the region between the plates is filled with a material of dielectric constant k. the potential difference across the capacitors now becomes
[a]2V/K [b]3V/K
[c]3V/[K+2] [d]2V/[K+3]
Q.19 A parallel plate capacitor is charged and then the charging battery is disconnected. If the plates are moved farther apart by means of insulating handles
[a] the charge on the capacitor increases
[b] the voltage across the plates increases
[c]the capacitance increases
[d] the electrostatic energy stored in the capacitor increases
Q.20 A parallel plate capacitor has plate area A and separation d and is charged to potential difference V0. the charging battery is disconnected and the plates are pulled apart to 3 times the initial separation. The work required to separate the plates is
[a] [b]
[b]
[c] [d]
[d]
Q.21 The radius of the air layer between the two coatings of the spherical capacitor is 2cm. the capacitor has the same capacity as spheres of diameter 120cm. the radius of the outer coating is
[a12cm [b]10cm
[c]24cm [d]16cm
1 comments:
Where are the answers...???
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