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HOLIDAY HOMEWORK
SUB: PHYSICS
STD – XII
1. What is quantization of charge?
1.
What are the basic properties of charge?
2.
When a glass rod is rubbed with silk, the glass rod gets positive charge. Why?
3.
What is the nature of charge on an ebonite rod, when it is rubbed with cat skin?
4.
Define one coulomb.
5.
State Coulomb’s law of electric force.
6.
State the law of conservation of charge.
7.
What is the effect of speed on the charge and mass of a charged particle?
8.
Is electrostatic force a central force? Justify.
9.
What is the charge of a neutron?
10. What is the magnitude and nature of charge on a proton?
11. What is the charge on the nucleus of a helium atom?
12. Define an electric line of force.
13. Find the number of electrons that constitute one coulomb.
14. Draw electric field lines to represent a uniform electric field.
15. Draw lines of force to represent the electric field due to a (i) positive point charge
(ii) negative point charge.
16. Write the characteristics on electric lines of force.
17. Two lines of force never intersect each other. Why?
18. Does electrostatic force obey Newton’s third law of motion?
19. Write the value of Coulomb constant (k) in SI unit.
20. Write the value of permitivity of free space in SI units.
21. Define dielectric constant of a medium in terms of force between electric charges.
22. Find the ratio of the order of magnitude of electrostatic force to gravitational force.
23. Why metals are good conductors and rubber is an insulator?
24. Two identical metal spheres carrying unequal positive charges, are separated by a certain distance.
They are brought together in contact and separated to the same distance apart as before. What will
happen to their charges and the force between them?
25. Why the charge on a body cannot be less than the electronic charge?
26. What is the effect on the electrostatic force between two charges if (a) a dielectric slab is
introduced between them (b) A metal slab is introduced between them
27. What is an electric dipole?
28. Define electric dipole moment. Write its unit.
29. Define electric field strength. Write its unit. Is it a scalar or a vector?
30. Define electric dipole moment in terms of torque.
31. What is the electric field intensity at the centre of a uniformly charged ring?
32. Draw lines of force due to (a) two equal and opposite charges separated by a small distance. (b)
two equal and similar charges separated by a small distance.
33. Write the expression for torque experienced by a dipole in a uniform electric field. When is the
torque maximum?
34. What is the net force acting on a dipole of dipole moment P placed in a uniform electric field of
intensity E.
35. Define electric potential at a point.
36. What is an equipotential surface?
37. What is the shape of equipotential surfaces due to a point charge?
38. write the SI unit of electric potential? Is electric potential a scalar or a vector?
39. Define electric potential energy of a charge at a point in an electric field.
40. How does the electric field due to a long, thin uniformly charged conductor vary with distance?
41. Define electric flux.
42. State Gauss Theorem.
43. What is electrostatic shielding?
44.
What is the value of the electric field outside the region enclosed by two infinite plane sheets
having charge densities ? & -?
45. What is the electric field at any point between two infinite plane parallel sheets having charge
densities ? & -?
46. If coulomb’s law involved 1/r3 dependence, would Gauss law still hold?
47. How does the electric field (E) vary with distance (r) in the following cases
(a) Uniformly charged spherical shell
(b) Uniformly charged solid sphere
(c) Uniformly charged plane sheet of large size.
Also plot a graph between E and r in each case.
48. What are dielectrics?
49. Distinguish between polar and non polar dielectrics.
50. Define capacitance of a conductor and write its SI unit.
51. Define one farad.
52. What is a capacitor?
53. Write an expression for the capacitance of a parallel plate capacitor.
54. What is the effect on the capacitance of a capacitor if the space between the plates is filled with
dielectric medium of dielectric constant K.
55. Define dielectric constant.
56. Three capacitors of capacitances C1, C2 and C3 are connected in (i) Series (ii) Parallel. Write the
expression for the equivalent capacitance in each case.
57. In which form is energy stored in a capacitor?
58. The plates of a capacitor of capacitance C are charged to a potential V. Write an expression for the
energy stored in a capacitor.
59. What is the effect of temperature on thedielectric constant of a dielectric medium?
60. How will the capacitance of a parallel plate capacitor be affected if (i) the area of each plate is
increased (ii) the distance between the plates is increased?
61. Name the different forms of energy into which the electrical energy of the atmosphere is dissipated
during lightning?
62. What orientation of an electric dipole in a uniform electric field corresponds to its stable
equilibrium?
63. What is the ratio of electric field intensities at any two points between the plates of a parallel plate
capacitor?
64. What is the amount of work done in moving a 100 nC charge between two points 5cm apart on an
equipotential surface?
65. How does the force between two point charges change if the dielectric constant of the medium in
which they are kept increases?
66. Name the Physical quantity whose SI unit is
1.
newton/coulomb
2.
joule/coulomb
67. In a medium, the force of attraction between two point electric charges. distance d apart is F. What
distance apart should these be kept in the same medium so that the force between them becomes
1.
3F
2.
F/3
68. In which direction does the electric potential decrease in a uniform electrostatic field?
69. Draw graph showing variation of electric field with distance for a uniformly charged metallic
sphere.
70. Write down dimensional formula for K (*the proportionality constant in Coulomb’s law)
71. What will be the dimensional formula for electric field?
72. For what orientation does an electric dipole experience a zero torque but non zero force in a non
uniform electric field?
73. Define dielectric strength of a medium.
74. Show graphically the variation of charge Q with time t when a condensor (capacitor) is charged.
75.
Two point charges, q1 and q2 at a separation r in vacuum exert a force F on each other. What
should be their separation in an oil of relative permitivity 16 so that the force between them remains F
only.
76. What should be the charge on a sphere of radius 2 cm so that when it is brought in contact with
another sphere of radius 5cm carrying a charge of 10 microcoulomb, there is no net transfer of charge
between the spheres.
77. The dielectric constant of a medium is unity. What will be its permitivity?
78. How will the capacitance of a parallel plate capacitor be affected if (a) The Area of each plate is
increased (b) The distance between each plate is increased
79. Name the different forms of energy into which the electrical energy of the atmosphere is dissipated
during lightning.
80. What is a gold leaf electroscope?
81. What do you mean by additivity of charge?
82. State the principle of superposition of electric forces.
83. What is electric p[olarisation? Define polarisation density.
84. State the principle of working of a Vam de Graff generator.
85. Distilled water is an insulator, but impure water is a conductor. Explain why?
86. How will you shield a sensitive instrument from strong electric fields?
87. Write the expression for the capacitance of an isolated conducting sphere of radius r.
88. The electric field at a distance r from a short dipole on the axial position is E1 and at the same
distance on the equatorial position is E2. What is the relation between E1 and E2.
89. Charge q each is placed at the corners of an equilateral triangle of side a. What is the electric field
intensity at the centre of the triangle?
90. Write an expression for the work done in turning a dipole through and angle theta; from its stable
equilibrium position in a uniform electric field E
91. Calculate the electric field between two metal plates 3 mm apart connected to a 3V battery.
92. A point charge of 8.86 C is placed at the centre of a cube of side 10 cm. Calculate the flux passing
through its one face.
93. What is the area of the plates of a parallel plate capacitor of capacitance 2F and with separation
between plates 0.5 cm?
94. How does the potential V due to short electric dipole on its axis vary with distance r from the
centre of the dipole?
95. Are there points around a dipole where the electric field is not zero but potential due to it is zero?
96. Can the electric potential at a point be zero where the electric field is not zero?
97. Can the electric field at a point be zero where the potential is not zero?
98. What is the nature of electric field between the plates of a parallel plate capacitor?
99. What is the relation between absolute permitivity and relative permitivity of a medium?
100. What is the direction of electric field at a point on the equatorial line of a dipole.
101. What is the angle between the directions of electric field at two points A and B due to an electric
dipole if A is on the axial position and B is on the equatorial position.
102. How much work is done in deflecting an electric dipole of dipole moment p in a uniform electric
field E through 180 from the equilibrium position?
103. An electron and proton are free to move in an electric field. Which one will have greater
acceleration? Why?
104. Write two uses of a capacitor
105. Define dielectric constant of a medium in terms of capacitance.
106. How is the electric field at a point related to potential at that point?
107. The electric field is discontinuous across the surface of a conductor. Is the electric potential also
discontinuous?
108. Sketch two equipotential surfaces for (a) a point charge. (b) between two plane sheets of charge.
109. What is the work done in carrying a point charge 10 nC between two points separated by a distance
5 cm on an equipotential surface?
110. Two point charges of unknown magnitude and sign are placed certain distance apart. The electric
field is zero at a point not between the two charges but at a point on the line joining them. Write two
essential conditions for this to happen.