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—, , , , , , SECTION A:, , Electric Charge, , 1. Ifa body is charged by rubbing it. Its weight, , — (a) always decreases slightly, (b) always increases slightly y, (g) may increase slightly or may decrease slightly, (d) remains precisely the same, , 2. In general, metallic ropes are suspended on the carriers, — which take inflammable material. The reason is, (a) There speed is controlled, (b) To keep the centre of gravity of the carrier nearer to, the earth, (c) To keep the body of the carrier in contact with the, earth, (d) Nothing should be placed under the carrier, , 3, Four metal conductors having different shapes, 1. A sphere 2. Cylindrical, 3. Pear 3. Lightning conductor, , Are mounted on insulating stands and charged. The one, which is best suited to retain the charges for a longer time, , is, , (a) 1 (b) 2, (©) 3 _@4 |, , 4. What is the amount of charge possessed by 1 kg of, electrons? i, , Given that mass of an electrons is 9.1 x 107! kg., (a) 6.25 10°C — (b) 1.76 10''C, (c) 1.76 x 10°C = (d) 1.25 x10C, , 5. A polythene piece rubbed with wool is found to have, negative charge of 3.6 x 107 Cc. a the number, , 4, , TOPICWISE QUESTIONS, , from wool to polythene. If, , of electrons transferred, 9.1 x 107! kg, find the mass, , an electron has_a mass, transferred to polythene., (a) 2.25x10'°kg, (c) 2.05 x10? kg, , (b) 6.25 x 10"? kg, (d) 4.15 x 107 ke, , . There are two metallic spheres of same radii but one is, , solid and the other is hollow, then, , (a) Solid sphere can be given more charge, (b) Hollow sphere can be given more charge, (c) They can be charged equally (maximum), (d) None of the above, , . When a body is earth connected, electrons from the earth, , flow into the body. This means the body is....., (a) Unchanged (b) Charged positively, (c) Charged negatively (d) an insulator, , . A positively charged insulator is brought near (but does, , not touch) two metallic sphere that are in contact. The, metallic spheres are then separated. The sphere which, was initially farthest from the insulator will have:, , (a) no net charge (b) a negative charge, , (c) apositive charge, , (d) either a negative or a positive charge., , . Suppose we have a large number of identical particles,, , very small in size. Any of them at 10 cm separation repel, , with a force of 3 x 107° N. If one of them is at 10 cm, , from a group of n others, how strongly do you expect it to, , be repelled?, , (a) 3x 10-°N, 10, , (c) Sn N, , n, , (b) 3nx 107° N, , (d) can not be calculated

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1.2. Physics, , 10. An uncharged metal object M is insulated from its, surroundings. A positively charged metal sphere S is then, brought near to M. Which diagram best illustrates the, resultant distributions of charge on S and M ?, , , , (b), , , , (©), , , , (d), , 11. Five balls numbered 1 to 5 are suspended using separate, threads. Pairs (1, 2), (2, 4) and (4, 1) show electrostatic, attraction, while pair (2, 3) and (4, 5) show Tepulsion., Therefore ball 1 must be, (a) Positively charged (b) Negatively charged, (c) Neutral (d) Made of metal, , 12. A point charge + q is placed at a distance d from an, , isolated conducting plane. The field at a point P on the, , other side of the plane is, , (a) directed perpendicular to the plane and away from, , the plane, , b) directed perpendicular to the plane but towards the, , Bane, , ) directed radially away from the point charge, , directed radially towards the point charge, , cases, two identical conducting spheres are given, , in one case of the same type whereas in, , of opposite type. The distance between the, ot large comparing with the diameter. Let, , he magnitude of the force of interaction, , a8 shown, then, , --@@--F, ee, , Fg Re, , , , , , , , , , (a) F,>F,, () Fy=F,, (c) F,<F,, (d) information is not sufficient to draw the conclusion, , 14. The diagram shows the arrangement of three small, uniformly charged spheres A, B and C. The arrows indicate, the direction of the electrostatic forces acting between the, spheres (for example, the left arrow on sphere A indicates, the electrostatic force on sphere A due to sphere B), At, , 16., , 17., , 18., , least two of the spheres are positively charged, Which, sphere, if any, could be negatively charged?, , A |, ia, , (b) sphere B, (@) no sphere, , (a) sphere A, (c) sphere C, , iS. The velocity of an electron at point A, is Vy where cross, , sectional area is A. The velocity of electron just the end of, contraction at point B, where cross sectional area is 2A, is, V,. Find the correct option:, , e tee, , hn Sw", (a) Vi< Vo (b) V;=Vo, Vy, (©) VYi>V @ h=>, , A glass rod rubbed with silk is used to charge a gold leaf, electroscope and the leaves are observed to diverge. The, electroscope thus charged is exposed to X-rays for a short, period. Then, , (a) The divergence of leaves will not be affected, , (b) The leaves will diverge further, , (c) The leaves will collapse, , (d)_ The leaves will melt, , One metallic sphere A is given positive charge whereas, another identical metallic sphere Bof exactly same mass, as of A is given equal amount of negative charge. Then, (a) Mass of A and mass of B still remain equal, , (b). Mass of A increases, , (c) Mass of B decreases, , (d) Mass of B increases, , A charged metallic ball is lowered into an insulated metal, can,, , a. thread, , , , The ball is made to touch bottom of the can. then it is, , Placed on the disc of electroscope shown below. Final, observation must be

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(a) leaves of electroscope diverges, , (b) leaves of electroscope converges, , (c) leaves of electroscope remains unaffected, (d) leaves of electroscope oscillates, , EE, , 19. Anelectroscope is given a positive charge, causing its foil, leaves to separate. When an object is brought near the top, plate of the electroscope, the foils separate even further., We conclude, , , , (a) that the object is positively charged., (b) that the object is electrically neutral., (c) that the object is negatively charged., (d) none of these, , 20. Given are four arrangements of three fixed electric, charges. In each arrangement, a point labelled P is also, identified — test charge, +g, is placed at point P. All of, the charges are of the same magnitude Q, but they can be, either positive or negative as indicated. The charges and, point P all lie on a straight line. The distances between, adjacent items, either between two charges or between a, charge and point P, are all the same., , 1@O@Oz 1 OO30, 1@@O@; O00;, , Correct order of choices in a decreasing order of, magnitude of force on P is, (a) I>I>MI>IV, (c) W>I>IV>Il, , 21. An electrically isolated hollow (initially uncharged),, conducting sphere has a small positively charged ball, suspended by an insulating rod from its inside surface,, , see diagram., , , , , a, , :, :, ., , (b) I>U>M>IV, (d) WI>IV>1>0, , , , , , causes the inner surface of the sphere to become, When the ball is centred in the sphere, , ide the conducting sphere is, , , , This, negatively charged., the electric field outs’, (a) zero, (b) the same as i, (c) twice what it wou!, (d) equal in magnitude but oppo:, it would be if the sphere wasn’t there, , f the sphere wasn’t there, Id be if the sphere wasn’t there, site in direction to what, , Electric Charge, Field ond Flux 1.3, , 22. A thin metallic spherical shell contains a charge Q on it., A point charge g is placed at the centre of the shell and, another charge g; is placed outside it as shown in Fig. All, the three charges are positive., , Q, , The force on the charge at the centre is, (a) towards left (b) towards right, (c) upward (d) zero., , B. A copper sphere of mass 2.0 g contains about 2 x 10”, atoms. The charge on the nucleus of each atom is 29e, (e = electronic charge). The mass: of-an electron is, 9.11 x 10! kg. How much mass will the sphere lose or, gain if-it isa given a charge of +2 HC?, (a) Loss a mass of 1.33 x 107%, (b) Gain a mass of 1.13 x 107g, (c) Neither gain nor loss any mass, (d) Change in mass will depend upon the kinetic energy, , of the electrons, , 24. Assume that each of copper atom has one free electron., Estimate the number of free electrons in 1 mg of copper., Given that atomic weight of copper = 63.5 and Avogadro, number = 6.02 x 107°. What is the charge possessed by, these free electrons?, (a) 1.52C (b) 1.76C, (c) 4.76C (d) 1.25C, , 25. Estimate the number of free electrons in 1g of water, and the negative charge possessed by them. Given that, Avogadro number = 6.02 x 10” and molecular weight of, water = 18., , (a) 6.25 x 10°C, (c) 1.76 x 10°C, , (b) 5.35 x 10°C, (d@) 1.25x 10°C, , Coulomb’s Law, , 26. Three point charges are placed at the corners of an, equilateral triangle. Assuming only electrostatic forces, are acting., , (a) the system can never be in equilibrium, , (b) the system will be in equilibrium if the charges, rotate about the centre of the triangle, , (c) the system will be in equilibrium if the charges have, different magnitudes and different sings, , (d) the system will be in equilibrium if the charges have, the same magnitude but different signs.

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aoe, , , , 1.4. Physics, , 27. Two identical simple pendulums, A and B, are suspended, , from the same point. The bobs are given positive charges,, with A having more charge than B. they diverge and reach, equilibrium, with A and B making angles 0, and 0, with the, vertical respectively. Which of the following is correct?, (a) 0,>%, (b) <®, © 6=%, (d) The tension in A is greater than that inB., , 28,//Two identical conducting spheres having unequal positive, charges q, and q, separated by distance r. If they are made, to touch each other and then separated again to the same, distance. The electrostatic force between the spheres in, this case will be (neglect induction of charges), (a) less than before (b) same as before, (c) more than before (d) zero, , 29. Two point charges placed at a distance rin air experience, a certain force. Then the distance at which they will, experience the same force in a medium of dielectric, , constant K is, (a) 7K (b) Kr °, © ar (@ r+VK, , Two copper balls, each weighing 10g are kept in air 10cm, apart. If one electron from every 10° atoms is transferred, from one ball to the other, the coulomb force between, them is (atomic weight of copper is 63.5), , (a) 2.0 10'°N (b) 20x 10°N, , () 20x 10°N (@) 2.0x 10°N, , What is the Coulomb’s force between two a-particles, separated by a distance of 3.2 x 10° m., , (a) 90N ~ (b) 45N, , (c) 60N_ (d) 75N, , Force of attraction between two point electric charges, placed at a distance d in a medium is F. What distance, apart should these be kept in the same medium, so that, , 30., , 31., , 32., , force between them becomes F/3?, (a) 23d (b) 3d, (©) 9d @ VBd, , 33. Two identical balls each have a mass of 10g. What, charges should these balls be given so that their interaction, equalizes the force of universal gravitation acting, between them? The radii of the balls may be ignored in, comparison to distance between them,, , (a) 6.34x10'C (b) 8.57x 10", , (©) 634% 10-7 C (4) 857x103 .¢, , 34, Two point charges +3 1C and +8 UC repel each other with, , a force o! 40 N, If a charge of -5 C is added to each of, th on , then the force between them will become, , (b) +10N, (d) -20N, , , , , , , , 35., , 37., , 38., , 39., , 40., , 41, , 42,, , charges 5.0 x 10NC ang, The distance at which a third, r that it will not experience, the two charges is, , (b) 0.65 m, , (d) 0.350 m, , Jectrostatic to gravitational force, ced at certain distance in air, 107! kg, € = 1.6 x 10" C ang, , tween, , 0.2 m., Jaced in orde!, , e line joining, , 5 bet, distance ©, ™" x 101 Cis, charge should, any force along th, (a) 044m, (c) 0.556 m, , Given that Me 9?, , G=65% 10, NmXe (3.210%, , (a) oe 10” (d) 1.2x 10, , © * and +e are kept 16 cm. apart, , * le, , Two ba eS should a third charge q be placed, from enn fa that the system is in equilibrium state ;, Oo from +9¢ (b) 12cm from +9e, , : Bs cm from +€ (d) 12cm from +e, , ‘Two spherical conductors B and C having equal radii, and carrying equal charges 1n them repel each other, , with a force F when kept apart at some distance. A third, spherical conductor having same radius as that of B but, uncharged is brought in contact with B, then brought in, contact with C and finally removed away from both. The, new force of repulsion between Band Cis, , (a) F/4 (b) 3F/4, , (c) FI8 (d) 3F/8, , Two equally charged, identical metal spheres A and B, repel each other with a force ‘F’. The spheres are kept, fixed with a distance ‘r’ between them. A third identical,, but uncharged sphere C is brought in contact with A and, then placed at the mid-point of the line joining A and B., The magnitude of the net electric force on C is, , (a) F (b) 3F/4, , (c) FR (d) F/4, , What equal charges would have to be placed on earth and, moon to neutralize their gravitational force of attraction?, om ae mass of earth = 10° kg and mass of moon, = 2., , (a) 8.57x 10'%C (b) 857x102, , (©) 5.45x 10% (@) 5.45 x 10°C, , Three charges 4g, Q and q are in a straight line in the, , Position of 0, 1/2 and J i, qwill be zero, if os respectively. The resultant force on, , <9 (b) -24, (c) wll, 2 (d) 4q, ‘TWo small bs i, on each balls having equal positive charge Q (coulomb), , au me by two insulated string of equal, , ae ems a hook fixed to a stand. The whole, , once Satellite into space where there is 0, , _ eightlessness). Then the angle betwee?, tension in the string is, , length 1, set up is, Bravity (g, the String

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43., , 45., , 47., , , , , , @) 1802,1__2, , , , . 1 @, by 90°,, © ° Ane, , , , Ame) (2LY » LE, -_1 @ 1 QL, (ce) 180°, —. 2 d) 180° 2, 4ne€, 217 @ BO ye, AE, , Two similar spheres having +q and —q charge are kept ata, certain distance. The force acts between the two is F. If in, the middle of two spheres, another similar sphere having, +q charge is kept, then it experience a force in magnitude, and direction as a, , (a) Zero having no direction, , (b) 8F towards +q charge, , (c) 8F towards —g charge, , (d). 4F towards +q charge, , Point charges +4q, -q and +4g are kept on the x-axis at, points x = 0, x = a and X = 2a respectively, then, , (a) Only q is in stable equilibrium, , (b) None of the charges are in equilibrium, , (c) All the charges are in unstable equilibrium, , (d) All the charges are in stable equilibrium, , Two identical balls having like charges and placed at, a certain distance apart repel each other with a certain, force. They are brought:in contact and then moved apart, to a distance equal to half their initial separation. The, force of repulsion between them increases 4.5 times in, comparison with the initial value. The ratio of the initial, , charges of the balls is ., (a) 2 (b) 3, (c) 4 (d) 6, , Two charges +4e and +e are ata distance x apart. At what, distance, a charge q must be placed from charge +e so, that it is in equilibrium, , (a) x/2 (b) 2x/3, , (c) x3 (d) x/6, , Charges 4Q, q and Q and placed along x-axis at positions, x=0,x= 1/2 and x=, respectively. Find the value of q, so that force on charge Qis zero, , (a) Q (b) Q/2, , (©) - Q/2 (d) -2, , Two equal negative charges —q are fixed at points (0, a), and (0, — a) on the y-axis. A positive charge Qis released, from rest at the point (2a, 0) on the x-axis. The charge, , Qwill, , 49., , 50., , 51., , 52., , 53., , Electric Charge, Field and Flux 1.5, , (a) Execute simple harmonic motion about the origin, (b) Move to the origin and remains at rest, , (c) Move to infinity, , (d) Execute oscillatory but not simple harmonic motion., Electric charges of 1 wC, -] #C and 2 1C are placed in, air at the comers A, B and C respectively of an equilateral, triangle ABC having length of each side 10 cm. The, resultant force on the charge at C is, , (a) 09N (b) 1.8N, , (c) 2.7N (d) 3.6N, , Three charges each of magnitude q are placed at the, comers of an equilateral triangle, the electrostatic, force on the charge placed at the centre is (each side of, triangle is L), , , , , , 1 g¢, , (a) Zero ‘’b) ——+>, ©) Ane D>, , 1 3q 1 ¢, , ©) — = d +, Ane D 2 127€), , Equal charges q are placed at the four corners A, B, C.D,, , of a square of length a. The magnitude of the force on the, , charge at B will be, 2, , , , , , , , , , (a) 34 ; o 2 Ane a’ Aneya”, 2 2), (©) 1422 \_a? @ (24-L\_4, 2 J Ameya” V2) Aneqa?, , Charges Q, -q, Q, -q are placed at the corners A, B, C,, D of a square respectively. If the resultant force on the, charge Q is zero due to other charges, what is the relation, between Q and q?, , (a) Q=-2V2q, () Q=-V2q, , (b) Q=-2q¢, , 1, (d) ee, o=- 3B!, , An infinite number of charges, each of charge 1 WC, are, placed on the x-axis with co-ordinates x = 1, 2, 4, 8, ....0%, Ifa charge of 1 C is kept at the origin, then what is the net, force acting on | C charge, (a) 9000 N, , (c) 24000 N, , (b) 12000 N, (d) 36000 N