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Conservation of electric charge implies that:, , (A) charge exists on particles, , (B) charge cannot be destroyed, , (C) simultaneous creation of equal and opposite, charges is permissible, , (D) the number of charged particles in the, universe is constant., , Quantization of charge implies :, (A) charge exists on particles, , (B) there is a minimum permissible magnitude, of charge, , (C) charge, which is a fraction of coulomb,, Is not possible, , é) (D) none of the above., , us ae of the two charges is doubled, the distance of their separation is also, , gated. The electrostatic force between them, , (A) be halved (B) be doubled, (C) become four times, (D) remain unchanged., , . 108, 4 i electrons are added to a pith ball. The, arge on the pith ball will be :, , (A) 16x 10-136 (B) 16x 10-19C, (C) 1.6 10-25¢ (D) none of the above., , 5. 6, ce electrons are taken out of a pith ball. The, ‘@rge on the pith ball will be : /, , (A) 16x 10-2 (B) 1-6 x 10-19, , (C) 16x 10-136 (D) none of the above., , 3. The minimum, amoun|, faris: it of charge observed so, , (A) 1C, , (B) 48x 10-3¢, (C) 1-6 x 10-19.¢, , (D) none of the above., , , , 10., , 11., , Objective Physics ——, , (C) Negative charge is induced on the leaves, , (D) Positive charge is induced on one leaf, , and negative charge is induced on the, , other leaf., , Mid way between the two equal and similar, , charges, we place the third equal and similar, , charge. Which of the following statements is, , correct ?, , (A) The third charge experiences a net force, inclined to the line joining the charges., , (B) The third charge is in stable equilibrium, , (C) The third charge is in unstable equilibrium, , (D) The third charge experiences a net force, perpendicular to the line joining the, charges., , Two charges are placed a certain distance apart., , A metallic sheet is placed between them., , What will happen to the force between the, , charges ?, , (A) Increases (B) Decreases, , (C) Remains unchanged, , (D) May increase or decrease depending on, the nature of metal., , Two charges are placed at a certain distance, , apart. If dielectric slab is placed between them,, , what happens to the force between the, , charges ?, , (A) Increases (B) Decreases, , (C) Remains unchanged, , (D) May increase or decrease depending on, the nature of the dielectric., , Two charges of 2uC and 5yC are placed, , 2-5 cm apart. The ratio of the Coulomb's force, , experienced by them is :, , , , i Positively charged glass rod is brought near oe pees, The fee wane gold leaf electroscope. (C) J2:/5 (D) 4:25, satire tele reap oe of the following (2) ne dielectric constant of an insulator cannot, (A) No charge is present on the leaves (A), 15 (B) 3, (B) Positive charge is induced on the leaves (C) 4-5 (D) «,, 1. (C) 2. (B) 3. (0) 4.1) 5.10) 6. {C) 7. (B) 8. (Cc) ‘9. (8) 10. (B), 11, (A) 12, (D), , , , , , v4

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—— Coulomb’s Law, , , , , , he permittivity of vacuum is :, (A) 1, , (B) more than 1, Cy less than 1 but not zero, D) zero., , 14. Two charges q; and qp repel each other with a, force of 0-1 N. What will be the force exerted, by q; On qe, when a third charge is placed, near them ?, , (A) Less than 0-1 N, , (B) More than 0-1 N, , orn" N ;, ) Less than 0-1 N if q, and qp are similar, and more than 0-1 N if q; and qo are, , dissimilar., , 15. The ratio of the force between two charges in, vacuum at a certain distance apart to that, between the same charges, the same distance, apart in a medium of permittivity « is :, , (A) 6:1 (B) 1:¢, , (C) egie (D) none of the above., , What happens when charge is placed on a, soap bubble ?, (A) It collapses its radius increases, , (C) Its radius decreases, (D) None of the above., , 17. A positively charged rod is brought near an, uncharged conductor. If the rod is then suddenly, withdrawn the charge left on the conductor will, , be, , (A) positive (B) zero, , (C) negative (D) none, , 18. The electric force between two charges each, , equal to 3u.C, when placed in vacuum is 12N., , What will be the force between them, if the, , charges are embedded in a dielectric of constant, , 6?, , (A) 36N (B) 18N, , P7~\ (C) 2N (D) 1N, , (s) There are two charges +3 microcoulomb and, +8 microcoulomb. The ratio of the forces acting, , on them will be, , (A) 3:1 BA, , (C) 1:8 (D) 1:11., , 20. The ratio of the electric force between two, , protons to that between two electrons under, similar conditions is of the order of :, , , , , 3.10 4 (C) 15. (0), 22, (A,B,C) 23. (A) 24. IC), , 16. (B), 25. (B), , 17. (B), 26. (D}, , , , 21., , 22., , 23., , 24., , 25., , 26., , 4305-9, (A) 1042 (B) 1039, , (C) 1038 (D) 1., , What is the change in the weight of a body, which is charged by rubbing ?, , (A) Weight always decreases slighily, , (B) Weight always increases slightly, , (C) Weight may increase or decrease slightly, (D) Weight remains precisely the same., , A charge Q is divided into two parts. Charge, , Q, ar 2. What is the, , Coulombic force between two charges q and q, , when both parts are placed certain distance, , apart ?, , (A) Force is equal in magnitude for both but, opposite in direction., , (B) Force is dependent on the medium in, which charges are placed., , (C) Force is maximum irrespective of medium, in which charges are placed., , (D) None of the above., , Two identical coins having similar charges are, placed 4.5 m apart on a table. Force of repulsion, , on each part is q. Also,, , 40, between them is 3° N. The value of charge, , on each coin is, , (A) 100pC (B) 200 pC, , (C) 300 nC (D) 400 pC, , When a glass rod rubbed with silk is brought, near the gold leaf electroscope, the leaves, diverge. What is the charge on the leaves ?, , (A) Negative (B) Equal and opposite, (C) Positive, , - (D) Either positive or negative., , In the above question, if the glass rod is brought, in contact with the disc of gold leaf electroscope,, the leaves diverge. What is the charge on the, leaves ?, , (A) Negative (B) Positive, , (C) Either positive or negative, , (D) Unpredictable., , What will be the change in the radius of a, soap bubble if it is given positive charge ?, , (A) The radius will decrease., , (B) The radius will remain unchanged., , (C) The radius may increase or decrease., , (D) The radius will increase., , 18. (C} Oe 20. (D} 21. (C)

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Dinesh Objective Physics ——, , , , 27. If acharge q3 is brought near one of charges qy,, q2, comprising a systerh, then what is the effect, of g3 on the force exerted by q; on q2?, , (A) The force due to q; on gz decreases., (B) The force due-to q; on qo increases., , (C) The force due to-.q; on gz remains, unaffected. od a, , (D) None of the above.», , 28. What is the ratio of forces acting on two charges, + 1 microcoulomb and — 5 micro coulomb ?, , (A) 1:5 (B) 5:1, (C) 1:10 Vt, , 29. Which among the following is a sure test of, electrification ?, , (A) Attraction (B) Induction, (C) Repulsion (D). Conduction., Questions From Competitive, A Examinations, wo charges qj, q2 are placed in vaccum ata, distance d, and the force acting between them, , is F. If a medium of dielectric constant 4 is, introduced around them, the force now will be, , , , (A) 4F (B) 2F, F F, (C) > (2) 7, (C.M.E.E. 1994), , 31. When 107? electrons are removed from a neutral, metal sphere, the charge on the sphere, , becomes, (A) 0-16 pC (B) -0-16 pC, (C) 0-32 pC (D) -— 0-32 pC, , (Manipal 1995), 32. If a soap bubble is charged with negative, charge, its radius, (A) will decrease, (C) will remain same, (D) data is not sufficient. (C.P.M.T. 1997), 33. Two charged spheres separated at a distance, d_ exert a force F on each other. If they are, immersed in a liquid of dielectric constant 2,, then what is the force (if all conditions are, same) ?, , (B) will increase, , , , 34. Number of electrons in one coulomb of charge, will be, (A) 5-46 x 1029, (C) 1-6 x 1019, , (B) 6-25 x 1018, (D) 9 x 1011,, (M.P.P.M.T. 1998), 35. The dielectric constant of metals is, (A) 1 (B) Greater than 1, (C) Zero (D) Infinite., (M.P.P.M.T. 1998), 36. The ratio of the forces between two tiny bodies, with constant charges in air and in an insulating, medium of dielectric constant ‘k’ is, (A) 1:k (B) k:1, (C) 1: (D) #:1., (C.E.E.T. 1998), 37. A body can be negatively charged by, (A) giving excess of electrons to it, (B) removing some electrons from it, (C) giving some protons to it, (D) removing some neutrons from it., (A.1.1.M.S. 1998), 38. When a positively charged conductor is earth, connected,, (A) Electrons flow from the conductor to the, earth, (B) No charge flow occurs, (C) Protons flow from the conductor to the, , earth, (D) Electrons flow from the earth to the, conductor (C.E.T. 1998), , 39. When air is replaced by dielectric medium of, constant k, the maximum force of attraction, between two charges separated bya distance, , (A) decreases k times, , (B) remains unchanged, , (C) increases k times, , (D) increases kK” times. (C.B.S.E. 1999), , 40. If the distance between two charges is doubled, and both the charges are also doubled then, the force between them will, , (A) be doubled : (B) remains the same, (C) become half... (D) become four times., , , , , , , (A) Fi2 (B) F, (c) 2F (D) 4F 41. A small uncharged metallic body is kept-near, a metallic rectangular-plate carrying a positive |, (A.LLM.S. 1997) charge. The electric force on the body, "97, (C) 28. (0) 29. (C} 30. 10) 3, A) * 32. 18) 33. (A) 34. 1B). 35, (D) 36. BI, "37, (AL 38. 1B) 39. (A) 40. (8). 41. A) :

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—— Coulomb’s Law, , , , , , (A) will be towards the plate, (B) will be away from the plate, (C) will be zero, (D) will be parallel to the plate., (H.P.P.M.T, 1999), , 42. A charged insulator is brought close to an, , uncharged metal., , (A) There is no electrostatic force between, them, , (B) There is electrostatic attraction between, them, , (C) There is electrostatic repulsion between, them, , (D) After sometime insulator gets uncharged, and metal gets charged., , (H.P.P.M.T. 2000), , 43. The scientist who experimentally showed that, , the electric charge is quantised only in terms, of integral multiples of electronic charge is, , , , 48., , 49., , 50., , Ci307~Y, When 10"? electrons are removed from a neutral, metal plate, the electric charge on it is (coulomb), (A) +1-6 iyat.e(B)-— 16, (C) 10-19 © (O) 1019, , +) \(Kamataka C.E.T. 1999), , A force of 40 N is acting between two charges, in air. If the space between them is filled with, glass with c, = 8, what will be the force ?, , (A) 15.N 2.(B) 320N, (C) 5N “(D) 32.N., at (J & KC.E.T. 2002), , Glass rod is rubbed with silk, both of them are, charged due to, , (A) Migration of protons, (B) Exchange of electrons and protons, (C) Migration of electrons, (D) Migration of neutrons., (E.A.M.C.E.T. 1981), , , , 52. 0) 53. (D), , (A) Max Born (B) Max Planck 51. Two point charges placed at a certain distance, (C) Thomson (0) Millikan ‘ apart in air, interact with a force F. If air is, (E). Einstein. (Kerala P.M.T. 2001) replaced by a medium of dielectric constant K,, 44. Two metallic spheres of same mass are given the force between them becomes/remains :, - equal and opposite charges, then: F, (A) the mass of positively charged sphere (A) F 8) K, increases, (B) the mass of both remains the same F, (C) the mass of negatively charged sphere (6). KF. (0) TK:, increases (Haryana C.E.E.T. 2002), (D) the mass of the both oe increases. 52. Two charges qj, q2 are placed in vacuum at a, P.E.T. (Raj.) 1991) distance d, and the force acting between them, 45. The ratio of gravitational force of interaction to is F. If a medium of dielectric constant 4 is, the, electric force of interaction between two introduced around them, the force now will be, electrons is of the order of : :, (A) 10-86 (B) 10-38 (A) 4F (B) 2F, (C) 10-42 . (D) 10-43 (C) F2 (D) F/4., (P.M.T. (Raj.) 1995) _ (Harayana C.E.E.T. 2002), 46. Unit of dielectric constant of a medium is 53. Assertion : The Coulomb force is dominating, (A) coulomb/newton-metre force in the universe., (B) newton-metre?/coulomb? Reason : The coulomb force is weaker than, (C) coulomb?/(newton-meter)? a ani : saa ies, ‘oth assertion and reason ai, (0) pelle ofthe above... (GE RET, 1283) the reason is the correct explanation of, 47. The ratio of the forces between two small assertion, spheres with constant charges (a) in air (b) in ., , i i ‘ i : (B) Both assertion and reason are true and, ee foe ee respectively the reason is not the correct explanation, a es et a4 of assertion, , »(D.P.M.T. 1998), 42. (B) 43. (D) 44. (C) 45. (0) 46. (0): 47. (8) 48. (A). 4% () 50. (C)_ 51. (8)

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(08>., , Dinesh Objective Physics, , , , , , (C) Assertion is true but reason is false, , (D) Assertion and reason are false statements., (A.1.1.M.S. 2003), , 54. The ratio of electrostatic and gravitational forces, , acting between electron and proton separated, , by a distance 5 x 10-''m, will be:, , (Charge on electron = 1:6 x 10719C, mass of, , electron = 9-1 x 10-91 kg, mass of proton = 1-6, , x 10-27 kg, G = 6-7 x 1071! Nm2/kg?), , (A) 2-36 x 1039 (B) 2-36 x 1040, , (C) 2:34 x 104 (D) 2:34 x 1042,, (Pubjab PM.T. 2003), , 55. When a body is earth connected, electrons from, , the earth flow into the body. This means the, body is, (A) Charged negatively, (B) An insulator, (C) Uncharged, (D) Charged positively., (Karnataka C.E.T. 2004), , , , 1-2. Knowledge based questions., , 3., , , , a Ne, mA 4neg, J _ 1 (2a)(2e), Ta% ‘Anco (2r =A, , 4nd 5. Charge on each electron is 1.6 x 10-9 C,, , x, , So, the charge added = 1-6 x 10-19 > x 108 =, 1-6 x 10-19 C., , Minimum charge is that on the electron., Knowledge based question., , The net force on the third charge is zero., However, when disturbed, the middle charge, can not return to the state of equilibrium., Because, the net force will not be zero anywhere except the mid point., , 9 and 10. The electrostatic force varies inversely, , 11., , 12., 13., 14., , 15., , as the dielectric constant. The dielectric constant, of the metals is very very large. So, the, electrostatic force will decrease., , Coulomb's interaction is in accordance with the, Newton's third law of motion., , Dielectric constant of conductor is infinite., , £9 = 8-854 x 10-12 C2 m=? N, Force between the two charges is independent, of the charges in its surroundings., , Fyacuurd Fmedium = €; = €/eo, | Answers], , 54. (A) 55. (D), , , , 16., , 17., 18., 19., , 20., , 21., , 23., , 24., , 25., , 26., , 27., , 28., , . Given,, , The electrostatic repulsion causes increase in, the radius., , Knowledge based question., , Fimedium = (1/k) Fyacuum, , The Coulomb's law obeys Newton's third law, of motion., , The magnitude of charge is same as that on, electron., , When a body gets charged after rubbing, then, either it becomes positively charged by loss of, electrons or it becomes negatively charged by, gain of electrons. Hence, its weight may increase, when it gains electrons or weight may decrease, due to loss of electrons., , . Q, PIAS, That is, the charge Q is divided equally into, two parts and therefore, force of repulsion, between both the parts is maximum. Also, it is, equal in magnitude but in opposite direction., , Given; F= 2, , 2.2, ae, , 40, , , , Vi, of 4neq oe te, 3 9 x.109 x, or aa clan Tage, . [Because, q = q2 = 4], > g = 10%, => : gq =10% C= 100nC, , The glass rod acquires positive charge on, rubbing. When the'rod is brought near the disc, of the electroscope, the disc will acquire negative, charge and there will be positive charge on, the far end, that is, on the leaves., , Due to conduction, positive charges of the glass, tod are passed on to the disc and leaves., , If a soap bubble is given positive charge, then, this charge is repelled by already existing, charge in the bubble. Hence, the radius of the, soap bubble increases due to repulsion., , The force due to qy on gz remains unaffected, because from the principle of superposition, it, , . is clear that force of interaction between any, , two charges’ is independent of other charges, present in the surroundings., Coulomb's force obeys Newton's third law of, , motion. Thats, it is equal and opposite between, , two charges. Hence, the ratio of forces is 1:1.