Electric Charges and Fields

ELECTRIC CHARGES AND FEILDS SECTION A: 1. 2. 3. 4. 5. 6. 7. 8. 9. State properties of charges and define them . What is elementary charge and what is its value? Define dielectric constant. What is SI unit of charge, force, elctric field, k and dielectric constt?Write their dimensional formula as well. Define electric field intensity. Define dipole moment (vector). What is direction of dipole moment? Define electric field. Define permittivity of free space. What is meant by conservation of charge? SECTION B: 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. What did Millikan oil drop experiment prove? Define pair production with energy condition. What is annihilation? Explain briefly. Why Coulomb force changes in dielectric medium? Why electric field lines never intersect? Why electric field inside conductor is zero? Define linear, surface and volume charge density. Why dipole moment is a vector? Why dipole has no net force in uniform field? State 4 properties of electric field lines. Why electric field is perpendicular to conductor surface? Compare electrostatic vs gravitational force (any 3). SECTION C: 22. 23. 24. 25. 26. 27. 28. Derive expression for electric field due to point charge. Define dipole moment and derive expression. Derive electric field of a dipole at axial and equatorial positions. Show relation between force and electric field. Explain inverse square nature of Coulomb force. Explain properties of electric field lines (any 3 with reason). Why electric field due to dipole decreases faster than point charge? SECTION D: 29. Derive Coulomb’s law (scalar + vector explanation). 30. Obtain relation between axial and equatorial fields. 31. Derive torque on dipole and obtain potential energy expression. VARDAANIYA CLASSES 1 32. Explain equilibrium positions of dipole with reasoning. SECTION E - NUMERICALS 33. Two charges (+4 μC) and (−2 μC) are placed 0.5 m apart in vacuum. Find the force between them. Also state its nature. 34. A point charge (+5 μC) is placed at origin. Find the electric field at a point whose position vector is Express your answer in vector form. 35. A charge (2 μC) is placed in an electric field Find the force acting on the charge. 36. Find electric field at a distance 0.2 m from a point charge (+2 μC). 37. A test charge moves from in a uniform electric field Find work done. 38. Two charges (+6 μC) and (−3 μC) are placed 0.3 m apart. Find the point on the line joining them where electric field is zero. 39. Two charges are located at Find the net electric field at origin. 40. Four charges each (+2 μC) are placed at corners of a square of side 1 m. Find electric field at the center. 41. Two equal charges (+q) are placed a (+a,0) and (-a,0). Find electric field at point ((0,b)) . 42. Two charges (+q) and (+4q) are 1 m apart. Find position where electric field is zero. 43. Three charges (+2 μC), (−1 μC), (+3 μC) are placed along a line. Find net electric field at a point between them. 44. Charges (+q, -q, +q) are placed at (0,0), (a,0), (0,a) Find electric field at ((a,a)). 45. An electric dipole consists of charges (±2 μC) separated by 4 mm. Find dipole moment. 46. A dipole of moment (p = 4×10-8 Cm) is placed in field . Find torque acting on it. 47. Find electric field at a point on axial line of a dipole at distance 0.1 m from its center. Find electric field at a point on equatorial line of same dipole as Compare with axial field. 48. Three identical charges are placed at vertices of equilateral triangle of side 1 m. Find net force on one charge using vector method. 49. A charge is moved from in field . Find work done. 50. A dipole with charges (+5 μC) and (−5 μC) separated by 2 mm is placed along x-axis. 51. Find electric field at point Express answer in vector form. 52. Four charges are placed at corners of square of side 0.5 m: Two opposite corners have (+q), the other two have (−q). VARDAANIYA CLASSES 2 53. Find: (a) Electric field at center (vector form) (b) Net force on a test charge placed at center (c) Explain symmetry used SECTION F - GRAPH BASED QUES. 54. Plot graph of electric field E vs distance r for a point charge. Indicate nature of variation and justify shape. 55. Plot graph of electric potential V vs distance r for a point charge. Compare with E vs r. 56. Sketch variation of force F vs distance r and r2 between two charges. 57. Plot graph of electric field E vs distance r for dipole on axial and equatorial line. 58. Plot variation of torque τ vs angle θ for dipole in uniform field. 59. Plot variation of potential energy U vs angle θ for dipole. 60. Draw electric field lines for: (a) single positive charge (b) single negative charge 61. Draw field lines for electric dipole and indicate direction. 62. Draw field pattern for two equal like charges. 63. Draw field pattern for two equal unlike charges. 64. Draw field lines between two parallel oppositely charged plates. 65. Explain why graph of E vs r for dipole falls faster than point charge. 66. Explain why electric field graph becomes zero at large distance for dipole. SECTION G: ASSERTION–REASON (Q65–Q70) Options: (A) Both true & R explains A (B) Both true but not explanation (C) A true, R false (D) A false, R true 67. Assertion: Charge is quantized Reason: Charge exists in multiples of e 68. Assertion: Electric field lines never intersect Reason: Field direction is unique 69. Assertion: Dipole has zero net force in uniform field Reason: Forces cancel 70. Assertion: Coulomb force is central force Reason: It acts along line joining charges 71. Assertion: Electric field inside conductor is zero Reason: Charges reside on surface VARDAANIYA CLASSES 3 72. Assertion: Dipole aligns along electric field Reason: Torque acts on it VARDAANIYA CLASSES 4