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PHYSIcs, , 4, 8., , 9., 10., , vIDYA Ma»Kmarks, , CLASS 12, A, , ELECTRICFIELD DUE TO, , SPHERICAL, , (i), , SHELL:, , Explanation : The net charge enclosed, , E =0, , must be zero and the charges outside the, , surface do not contribute to the electric flux., 5. In the given figure, two positive charges, 42 and 4s fixed along the y axis, exert a net, electric force in the +x direction on a charge, 41 fixed along the x-axis. If a positive charge, , SHELL:, OUTSIDE A SPHERICAL, , AdE = E.AS, , (i) ELECTRIC FLUX:, GAUSSS THEOREM, , Explanation: As, , oe E.S, So, it could be Vm equivalent of Nm/C, , 8., , A, , charge, , g, , is, , =, , placed, , at, , the, , point, , of, , intersection of body diagonals of a cube. The, electric flux passing through any one ofi, (Diksha), , face is, , (A)6E, , (B), , (, , (D), , Eo, , Qis added at (r, 0), the force on qu, , AE E.dS= E, , :, , 5, , Electric Charges And Flelds, Ans. (C) the number of flux lines entering the, surface must be equal to the number of, flux lines leaving it., , E =, , ELECTRICFIELD INSIDE A, ELECTRIC FIELD, , THIN, , FINITE SHEET:, , Ans. (A)Q =, , Competency Based Questions, , Explanation: The flux emerging through, surface encdosing charge q is given by, , x, , a, , :, , 13, , Multiple Choice Questions 1 Mark, 1. Ifa positive charge is displaced against the, electric field in which it was situated, then, (A) work will be done by the electric field, the charge, , on, , (B) the intensity of the electric field decreases, () energy of the system will decrease., (D) energy will be provided by external, source displacing the charge., CBSE 2020, set 5/3/1], Ans. (D) energy will be provided by external, source displacing the charge., , Explanation : Work will be done by, external electric field on the charge. As the, , positive charge placed in an electric field will, tend to move in the direction of the, field lines and a negative, charge will, move opposite to the direction of the, field lines., 2. If the net electric flux, through a, surface is zero, then we can infer:, , electric, tend to, electric, , Mistakes to Avoid, The point where electric field of system is zero, is not, necessarily the mid-point, , Draw the figure for approaching a easy method, calculation., , (B) 47, , C)E0, , D)E, , point, , to, , (D) charge is present inside the surface., ICBSE 2020, Set 55/1/1], Ans. (A) no net charge is encdosed by the surface., , Explanation, , :, , According, , the total electric flux, out of, is, equal to the net, , surface divide by the, , charge, , to gauss law,, , closed surface, enclosed in the, a, , permittivity., , CBSE 2020 Set 55/3/1, , Ans. (A), , and 9s, , Ans. (A) shall increase along the positive X-axis., , Explanation : Since, (+)ve charge qa and g3, exert a net force in +x direction on the charge, g fixed along the r-axis the charge q1 is (-)ve, as shown in figure, obviously due to addition, of (+)ve charge Q at (x, 0) the force on -q, shall increase along the (+)ve x-axis., 6. Which of the following figures represent the, electric field lines due to a single negative, charge ?, , 9. Electric charge between two bodies can be, , produced by:, (A) sticking, , (B) rubbing, , (C) oiling, , (D) passing AC current, , Ans. (B) rubbing., , Explanation:, , having lower, becomes, electrons, , The body, work function looses electron and, , positive, , and the other, , body gain, , become negative., 10. The electric flux due to a point charge, enclosed by a spherical Gaussian surface get, affected when its radius is increased:, (B) Increased, (A) Decreased, (C) No change, , (P) None of these, , Ans. (C) No change, , Explanation: There is nochange in electric, , Explanation:, Flux of a surface enclosing charge q 1s, , (A), , (B), , (C), , (D), , flux. When the radius of a spherical Gaussian, surface is increased, the charge enclosed by, the Gaussian surface remains the same., , =, , Here,, , 11. The electric flux through a cube of side 1 cm, which encloses an electric dipole is :, [Delhi 20151, , .., , Eo, , surface., , (C) electric potential varies from, point inside the surface., , of, , 3. The electric flux emerging out from 1C, charge is, , closed, , (A) no net charge is enclosed by the surface., (B) uniform electric field exists within the, , (D) shall increase but the direction changes, because of the intersection of Q with g2, , (AEnhance your Answer, , (A), , (A) shall increase along the positive x-axis, (B) shall decrease along the positive x-axis., (C) shall point along the negative x-axis., , 4. If, , Eds =0, , over, , a, , (A) Zero, (C) Two, , surface, then, , on it is zero., , (6) the electric field inside the surface l, necessarily uniform., (C) the number of flux lines entering the, must be equal to the number, surface, flux lines leaving it., , (D) None of the Above, , Ans. (A) Zero, , Ans. (B), , (A) the electric field inside the surface an, , o, , Explanation : As electric lines of forces, terminates at negative charge., 7. The SI unit of electric flux is, (A) NCm2, , (B) NCm, , (C) NC m, , (D) NCm, , Ans. (D) NC 'm*, , (B) One, (D) None of these, , Explanation: Since, netchargeenclosedin, the surtaces bound by cube is zero, as dipole, , consists of equal and opposite charge., , 12. If 10 electrons move out of a body to another, a, body every second, they required to get, total charge of 1 C o n the other body is

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vIDYA MaKmarks, CLASS 12, , | PHYSICS|, , 6, , charge on the pith ball will be:, (A) 1.6 x 10-13 c, (B) 1.6 x 10-19 C, , (D) 198 years, , (C) 194 years, , Fo, , (C) 1.6 x 10-25 C, , Ans. (D) 198 years, , Explanation: The charge given out in, , one, , = -1 x 10* x 8.85 x 10-12, , second,, 4, , =-8.85 nC., , ne, , q, , 1.6, , The time, , 10-19, , x, , required, , 10°'C =1.6, , x, , to, , get, , 1, *, , l.6, , x, , x, , 1o0C, , 0.4 HC due, charge, of charge - 0.8 C, , charge of1C, , a, , 6.25 x, , distance between, , 10s, , 10-10, , 6.25x 10, , = 198 years, , 365x 24 x 3600), 13. If, arbitary surface encloses a dipole, then, the electric flux through this surface is, (D) 3, (A) 0, (C) 2, (B) 1, an, , Ans., , force, 16. If the electrostatic, , on, , a, , small, , sphere of, , to another small sphere, in air is 0.2 N, then the, , spheres is:, , (A) 0.12 m, , (B) 0.012m, , (C) 1.12 m, , (D) 0.21 m, , Explanation:, 1 0 . 4uC, , 0.4, , =, , x, , 10- C, , 9x10" x0.4 x10, 2, , 0.2, , small charged, , 2 9 x 1 0 x0.4 x 10, , 30 cm apart in air is :, , (B) 5x 103N, , (C) 6x 103N, , (D) None of these, , N, , Explanation:, Force, , =, , 10, , x0.8 x 10, , x, , 10, , r 0.12 m, 17. Va and Vs are two points on a curved, equipotential surface, then relation between, Va and V is:, , 1 4192, 4TE, , 41= 2x 10 C,42 =3 x 107C, , 144, , Ans., , (A) VA<VB, , (B) Va> VB, , (C)VA=Vs, , (D) None of these, , (C) VA = Vs, , = 30 cm = 0.3 m, , 9x10' x2x10, , x3x10, , (0.3), , 10 N, , F 6x, 15. A point charge causes an electric flux of 1.0x, , 10 Nm'C, , to pass, , through a spherical, , Gaussian surface of 10.0 cm radius centered, on the, charge, then the value of the point, , charge is, , (A) 8.85 nCc, (C) 8.75 nC, Ans. (B)8.85 nC, , *For Detailed Solutions Scan, , (B) 8.85 nC, , (D)-8.75nC, , Explanation:, , Potential, , on, , each, , equipotential surface is constant., , point of, , Scan Yourself, 18., , Ans. (A) 1.6 x. 103 C, 20. Two charges are placed a certain distance, apart. A metallic sheet is placed between, them. What will happen to the force between, the charges ?, (B) Decreases, (A) Increases, (C) Remains unchanged, (D) May increase or decrease depending on, the nature of metal, , will be:, , The magnitude of the two, charges is doubled, and the distance of their separation is also, , doubled. The electrostatic force between, , them will:, , (A) be halved, (B) be doubled, , (C) become four times, , (D) remain unchanged, Ans. (D) remain, unchanged, , (B) 2F, (D) F/4, , (A) 4F, , (C) F/2, Ans., , (D) F/4, , 28. The ratio of electrostatic and gravitational, forces acting between electron and proton, will be:, a distance 5 x 10"m,, , separated by, , mass of, (Charge on electron =1.6 x 10"C,, electron = 9.1 x 10, kg mass of proton, , (A) 2.36 x 10, (C) 2.34x 10, 29. When, , near the gold leaf electroscope, the leaves, the charge on the leaves?, , diverge. What is, (A) Negative, , (B) Equal and opposite, C) Positive, (D) Either positive nor negative, Ans. (C) Positive, 24. If a soap bubble is charged with negative, charge, its radius, (A) will decrease, , (B) will increase, , (C), , will remain, , (D), , data is not sufficient, , same, , Ans. (B) will increase, 25. Number of electrons in one coulomb of, charge will be, , (A) 5.46 x 1029, (C) 1.6 x 10, , (B) 6.25 x 1018, , (D) 9x 10, , Ans. (B) 6.25 x 108, 26. The scientist who experimentally showed, that the electric charge is quantised only, in terms of integral multiples of electronic, charge is, , x, , 1040, , a, , body is, , earth connected, electrons, into the body. This, , (A) charged negatively, , Its radius increases, , Ans. (B) Its radius increases, 23. When a glass rod rubbed with silk is brought, , 2.36, , D) 2.34 x 102, , the earth flow, means the body is, , from, , (A) It collapses, , Its radius decreases, (D) None of the above, , B), , Ans. (A) 2.36 x 103, , soap bubble ?, , (B), (C), , in v a c u u m at, 42 are placed, distance d, and the force acting between, them is F. If a medium of dielectric constant, 4 is introduced around them, the force now, , Two charges 41, , = 1.6 x 1 0 kg, G = 6.7 x 10-1 Nm/kg), , less than 1 but not zero, (D) zero, Ans. (C) less than 1 but not zero, 22. What happens when charge is placed ona, , 0.2, , (A) 4x 10-3N, , Ans. (C) 6x 10, , x0.8x, , (D) Millikan, , a, , (C), , F4TE r, , surface is zero., 14. The force between two, spheres having charges of 2 x 10Cplaced, , 27., , (B) more than 1, , 42=-0.8 uC = - 0.8 x 106 C, , opposite charges. Therefore, the total charge, is zero. Therefore, the electric flux out of the, , of these, , Ans., , (A), , Force, F = 0.2N, , Explanation :Dipole consist of 2 equal and, , none, , (D) Millikan, , Thomson, , Ans. (B) Decreases, 21. The permittivity ofvacuum is:, , Ans. (A) 0.12 m, , (A) 0, , (D), , (B) Max Planck, , (A) Max Born, , 19. 10 electrons are added to a pith ball. The, , Explanation:, , (B) 192 years, , (A) 190 years, , 7, , Electric Charges And Fields, , (B) an insulator, , (C)uncharged, (D) charged positively, Ans. (D) charged positively, 30. Two helium nuclei are separated by a, distance 6 nm in vacuum. What is the, electrostatic repulsion between them ?, (A) 25.6 pN, , (B) 25.6 nN, , (C) 3.6 pN, , (D) 3.5 pN, , Ans. (A) 25.6 pN, 31., , A charge q is placed at the mid-point of the, , line joining two similar and equal charges, each equal to + 24C. The system will be in, equilibrium if q, (B) 1.0 uC, (A) -0.5 uC, =, , (C)+1.0 C, , (D) +0.5 uC, , Ans. (A) -0.5 C, , 32. Two equäl charges are separated by, distance d. A third charge placed on a, perpendicular bisector at x distance will, experience maximum coulomb force when, (A) x = d/W2, , (B)x =d/2, , x= d/22, , (D)r=d/2 3, , Ans. (C) x= d/2/2

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8, , PHYSICS, , VIDYA makmarks, , CLASS 12, , carrying equal, 33. Two vertical metallic plates, to each, are parallel, ball, and opp0site charges, , 37. ABCis right angle triangle with AB =3 cm., BC 4, , is, spherical metallic, a, long insulating thread, Suspended by, in the centre, other, , A small, , of, such that it hangs freely, which, the two metallic plates. The ball,, towards the, is uncharged, is taken slowly, is made to, and, positively charged plate, will, ball, Then, touch the, (A), (B), (C), (D), , stick, , plate., the positively charged plate, back to the original position, , to, , come, , and, , cm, AC = 5 cm. Charges 15, 12, 20, , coulomb are placed at A, B, C respectively, The magnitude of the force experienced by, the charge at B in newton is, , (A) 225, , x, , 125, , x, , (B), (C), , 25, , 1013, , 1013, , (D) O, Ans. (A) 225 x 1013, , oscillate between the two plates touching, , charge t 4. The latter is free to move only, , each plate in turn, , along the vertical direction. The charge, q is in equilibrium, because its weight is, balanced by the electrostatic attraction. In, which of the cases shown in answer figure,, the charge t 4 is in equilibrium ? The, separation between the charges remains, , oscillate between, touching them, , the, , plates, , without, , Ans. (D) oscillate between the plates without, touching them., of, 34. Three charges are placed at the vertices, 'a' as shown in, an equilateral triangle of side, the following figure. The force experienced, , by the charge placed at the vertex A in, direction normal to BC is:, , unchanged., , a, , of each, , (4TEo, , (B), , (D), , 13, , QT2, , 167t EgM, (B), , Q4T, , =, , 16 eM, , (A) 0.45 N, (C) 0.11 N, Ans. (D) 0.4N, , (B) 0.56 N, (D) 0.4N, , T2, , -T?, , 43. If a charge q is placed at the centre of the, line joining two equal charges Q such that, the system is in equilibrium, then the value, of q is, , The, , resultant, , to, , charges at B and, , force, , at, , O, , is, , on, , -4, , on, , -4 at O is, , 4TE h, (D) The, , resultant force, , along, , OC, , 4tE h, , Ans. (D) The resultant force on -4 at O is, , along, , 4TE0 h2, , OC., , P0, , eM, , 16 eM, , 3, in metres, , (-q) due, , 46. The charge density of a spherical charge, distribution is given by:, , (C)r16T eqM, 16, , X, , on, , E are balanced, , 1_alongOE, , 42. What is the relation between the radius of, the orbitr and the time period Tif a particle, ofcharge-gand mass M moves in a circular, orbit of radius r about a fixed charge +Q?, , (D), , (B) +4, , The force, , (C), , Ans. (D) r,, , Ans. (C), , below., , (C) Zero, , (A)r=, , what is the ratio Q/4?7, , D), , Coulomb are placed o n five vertices of a, regular hexagon of side h as shown in figure, , (B) ATEaL, , Ans.() 47e, , 39 The charges 4, 42,4s with respective valucs, 25 uC, 10uC, +20 HC are placed as shown, in the following figure. The resultant force, on the charge 4, will be, , Ans. (B) -Q/4, 36. Figure shows two, charges. If both the, charges, and q are in equilibrium, then, , (A)-, , (B) 12 cm from +9e, , 45. Five point charges each of charge +4, , (A) 43neg, , Ans., , (B) -0/4, D)+4Q, , Ans., , +, (A) The force on (-9) at O due to charges+9, at A and D are balanced, , Q, , (P), , (6), , (B)-4nga*), , system of three will be in equilibrium if q is, , Another, , (C), , () Zero, , (A) -Q/2, (C) +Q/2, , (A) 24 cm from + 9e, (B) 12 c m from + 9e, (C) 24 cm from +e, (D) 12 cm from +e, , (D) 20 and Q are placed at ends with Q, placed at 3 cm from 20., Ans. (D) 20 and Q are placed at ends with Q, placed at 3 cm from 202, 41. Five vertices of a regular hexagon of side, L are occupied by five point charges. The, value, point charge is +q., point charge-4 is placed at the centre of the, , point charges, , B, , -, , 35. If a charge q is placed at the centre of the, line joining two equal like charges Q. The, , +9e and + e a r e 16 c m, Where should another, from, each, other., away, them so that the, between, be, charge q placed, system remains in equilibrium ?, , 44. Two, , vertices of hexagon?, , -, , Ans. (C) Zero, , are to be placed on a straight line 9 cm long?, (A) 20 and 8Q are placed at ends with Q, placed 3 cm from 8Q., , (D) 0 / 4, , hexagon. What is the magnitude of the force, on -4 due to all the charges placed at the, , (A), , (A) Q(4a), , condition, , energy, if three point charges Q, 20 and Q, , (B) Q/2, , (A) Q/2, (C) Q/4, Ans. (D)-Q/4, , and 8Q are placed at ends with 20, placed at 6 cm from Q., (C) 20 and 8Q are placed at ends with Q, placed at 6 cm from 8Q, , 38. Fig. shows a fixed charge + Q and a movable, , will remain there, , 40. Which of the following conditions fulfil, the, of having minimum potential, , (B), , 1013, , x, , 9, , Electric Charges And Fields, , What is the total charge, (A) 2tn Po, , (B) 21tn Po, , (C) 4/3 tu pPo, , (D) 2/3nPo, Ans. (B) 27tn' Po, , r>n, , on, , the distribution?

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10, , VIDYA MaKmarksEleo, , PHYSIcs | CLASS 12, , drops of mercury, each of radius, charge q, coalesce to form a big drop., The ratio of the surface, each smaill drop with that of the big drop is, , 47., , 64, , CS, , r, , small, , and, , 56. If an electric dipole is placed in a uniform, electric field,, , it experiences:, , density of charge of, , Cs, , 10uC are suspended by two insulated, , found, , in equilibrium, threads are separated by an, , (B), , angle 60 between them as shown in figure., , 1, , 16, , 4TE 3 a2, , The tension in the thread is, (D) Zero, , 60, Ans. (D) Zero, 52. The electric field strength at a distancer from, a charge Q is E. What will be electric field, , if the, strength, distance of the, point is increased by 2x7, , field of intensity 20000 V/m. If mass of the, particle is 9.6 x 1071 kg the charge on it and, excess number of electrons on the, are respectively (g = 10 m/s):, , (A) 4.8 x 10" C, 3, , (C), , 3.8, , x, , 10- C,, , 2, , (D) 2.8, , x, , that at Pa, following statements is true?, 1, , 101 C, , 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 B and C is, , (B) 3F/4, , (C) F/8, (D) 3 F/8, Ans. (D) 3F/8, 51. In the basic CsCI, crystal structure, Cs' and, Ci ions are, in a bcc, arranged, configuration, as shown in the, figure. The net electrostatic, force exerted by the, eight Cs' ions on the C, ionsi is, , (A) E>Ez, (C) E E,/, , (A) intensity, (B) potential, (C) moment, (D) none of these, Ans. (A) intensity, 59. What does an electric charge in accelerated, motion produce ?, , (A) An electric field only, (B) A magnetic field only, (C) Electromagnetic radiation only, (D) All of the above, Ans. (D) All of the above, 60. A charge Q is placed at the corner of a cube., The electric flux through all the six faces of, the cube is, , (A) Q/E0, (C) Q/8 Eo, , (B) E> E, (D) E r'/E, , =, , (D) determining electric potential due to, symmetric charge disributions, Ans. (C) determination of electric field due to, symmetric charge distributions, 58. The force on a unit positive charge when, placed at any point in the electric field is, called:, , particle, , Ans. (A) 4.8 x 10-1° C, 3, 50. Two spherical conductors B and G, having, equal radii and carrying equal charges, on them, repel each other with a forceF, when kept apart at some distance. A third, , (), , observation, , (B) E/3, (A) E /2, (C) E/4, (D) none of these, Ans. (D) none of these, 53. The figure below shows electric field lines., field strength at Pi is E and, The electic, is E. If P,Pzis r, then which of the, , (B) 5.8 x 101° C, 4, , point charges, (B) situations where Coulomb's law fails, C) determination of electric field due to, symmetric charge distributions, , 32 e, , (C) 41tE0 3, , (A) 0.18 N, (B) 18N, (C) 1.8 N, (D) none of these, Ans. (C) 1.8 N, 49. A charged particle is suspended in, equilibrium in a uniform vertical electric, , (C) Cm, , :, , (D) Cm2, , Ans. (C) Q/8 E, 61. A charge q is placed at centre of the open end, of cylindrical vessel. The flux of the electric, field through the surface of the vessel is, , Ans. (A) Cm, 55. Which of the following does not, allow the, electric field lines to cross each other ?, , (A) They originate from positive, charge and, end at, , negative charge., (B) They do not pass through the conductor, (C) They exhibit longitudinal tension and, lateral pressure, , Superposition of electric fields., , Superposition, , (B) Q/6, (D) Q/3 o, , =, , Ans. (A) E, > E2, 54. The unit of electric dipole moment is, (A) Cm, (B) Cm2, , (D), Ans. (D), , then, , of electric fields., , (A) E, = 2E,, , (B) E, =2E, (C) E E, , (D) neither torque nor net force, , Ans. (A) torque only, 57. Gauss's law helps in :, (A) determination of electric force between, , threads of equal length 1m each, from a, that, point fixed in the ceiling. It is, , O, , on the equatorial line at the same distance,, , (B) net force only, (C) both torque and net force, , (D) 4:1, (C)1:4, Ans. (C) 1:4, 48. Two small sphere balls each carrying charg8e, , 4, , 62. If E be the electric field strength ofa short, that, dipole at a point o n its axial line and E,, , (A) torque only, , S, , (B) 1:64, , (A) 64:1, , 11, , Charges AndFFields, , (A) Zero, , (C)2, Ans. (C), , 2 Ep, , (), (D) 29, , =, , D) none of these, Ans., , (B) E, = 2E,, , 63. A dipole of moment p, electric field, , is placed in unite, , then torque acting on it is, , given by, (A), =P x E, , (B) T-P.E, , (C)T=P+E, (D) T= P- E, Ans. (B), , =, , P.E, , 64. Which of the following are not properties of, lines of forces in an electric field ?, , (i) Lines of force never intersect., (i) Lines of force start from negative charge, and terminate at the positive charge., (ii)The tangent to line of force at a point, gives the direction of the electric field., (iv) Each unit positive charge gives rise to, 4 T E unes ot torce in tree space., , (A) ), , and (iv), , (B) (üi) and (iv), , (C)i)and (ii), (D) (i) and (i), Ans. (B) üi) and (iv), 65. An electric dipole placed in a non-uniform, electric field experiences:, (A) both, a torque and a net force, (B) only a force but on torque, (C) only a torque but on net force, (D) no torque and no net force, Ans. (A) both, a torque and a net force, 66. The charged spherical shelf does not, produce electric field at any, (A) interior point, (B) outer point, (C) beyond 2 meters, (D) none of the above, Ans. (A) interior point

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VIDYA MaK markS, , 12 PHYSIcs | CLASS 12, 67. An uncharged sphere of metal is placed, The, inside a charged parallel plate capacitor., lines of force will look like, , ++++ +**, , Ans. (A)x (the change enclosed by surface), 71. What is the angle between the electric dipole, moment and the electric field strength du, , Electrile Charges, , And Fields, , 13, , 76. A metallic shell has a point charge 'q' kept, inside its cavity. Which one of the following, represents the electric, lines of forces ?, , diagrams correctly, , (A) 4.E and p.E, (B) zero and minimum, , (B) 90, , C) 180, (B), , (A), , (C) q.E and minimum, of these, , (D) 24.E minimum, , Ans. (A) 0°, 72. What is the ratio of two particles of masses, , (A), , (B), , m and 2m with charges 24 and 24 which, , (D), , (), , If its, , are respective, , (A) 0, , none, , electric field, , dipole moment is along the direction of the, , field, the force on it and its potential energy, , to it on the axial line ?, , (D), , 79. An electric dipole has the magnitude of its, charge as g and its dipole moment is p. It, E., is placed in a uniform, , Ans. (B) zero and minimum, 80. The variation of electric field intensity (E), with distance from centre of uniformly, , are placed in a uniform electric field E and, , charged spherical shell is best represented, , allowed to move for the same time?, , by which ofthe following graphs, , (A) 2:1, , (B) 8:1, , (C) 4:1, , (D) 1:4, , (D), , (C), , Ans. (A) 2:1, 73. A non-conducting sheet S is given a uniform, , charge density G. Two uncharged thin and, small metal rods X and Y are placed near the, Ans., , (A), , sheet as shown in the figure below. Which of, the statements given below is correct?, , 68. Electric field of an isolated holow metallic, sphere at any interior point is, (A) zero, (B) one, , Ans. (C), , 77. Shown below is a distribution of charges., The flux of electric field due to these charges, , Y, , through the surface is, , (A), , (B), , (C), , (D), , (C) proportional to field, (D) none of these, , Ans. (A) zero, 69. A charge g is placed at the centre of a cube., Then, the flux passing through one face of, , Ans. (C), (A) S attracts both X and Y, , (B) Yattracts both S and X, , B) 2E0, , hexagons, with, , (D) all of the above, Ans. (D) all of the above, 74. Apoint Q lies on the perpendicular bisector, of, , an, , electrical dipole of dipole momentp., , the distance of Q from the dipole is r (much, larger than the size of the dipole), then, , Ans. (D), , electric field at Q is proportional to, (A), and r2, , 6 Eo, , 70. If a spherical conductor comes out from the, , closed surface of the sphere, then total flux, emitted from the surface will be, , (A)(the, chargeenclosed by surface), 0, E, C) 4TE, , (B), , (D) 0, , 81. Figures below show regular, charges at the vertices. In which case is the, electric field at the centre zero ?, , (C) X attracts both S andY, , cube will be, , (charge enclosed by surface), (charge enclosed by surface), , (A), (A) 3q/Ep, , (B) 2/E, , (C) q/e, , (D) zero, , (C) p and, , field at a distance r from the centre of sphere, r>R) will be:, , Ans. (D) pand 3, , (A) DR, , 3e0, , 75. The dipole moment of a, dipole is 16 x 100 m, and is situated in an electric field of intensit, 10 V/m, its minimum energy will be, , pr, , :, , (A) -8 x 102, , (B) 16 x 102, , (C) 8 x 102, , (D) 16 x 102, , 2a, , (D), -2q 29, , radius R has charge density p. The electric,, , (D) p and r3, , Ans. (B) 16 x 102, , -29, , Ans. (D) zero, 78. If an insulated non-conducting8 sphere of, , (B) p and 7, , (B), , 29 9, , Ans. (A), , (B), , (D), , 82. A, B, C, D corners of a square are occupied, , 3pr, , 4,-, 22 and charges respectively., by, The side of sphere is 24. The field at the mid, point of side CD is zero. What is the value of, , Ans. (C), , 3E0

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VIDYA MaKmarkElectrlc Charges And Fields, , 14 PHYSIcs | CLASS 12, , 4, , (A) 9x 10°N/C, (B), , 2, , 22, , D), , (B) 9x 10 NC, , (B) /, , (C) 9x 10 NC, (D) 9x 10 NC, , (D) 20/Vol/meter, Ans. (C) /tg vol/meter, 93. The volume charge density has dimension:, (Diksha), , 86. Three positive charges of equal value, , 83. A charged cork ball having mass 1g and, in, q is suspended on a light string, charge, a uniform electric field as shown in figure., The ball is in equilibrium at 0 = 37, when, , are placed at the vertices of an equilatera, triangle. The resulting lines of force shoule, , (A)+,,t,-,-,+ (B) +,(C)+,+-,t,=,- (D) -,t, , be sketched as in, , Ans. (D)-,t,+,-,t,89. Above an infinitely large plane carrying a, charge density o. An electric field points up, , value of electric field is E =(3i+5)x 1, , (A) L-TA, (C)LTA, Ans. (C) LTA, , of the, (Given: sin 37 = 0.60 and g = 10 ms), , 2E0, , down, , (Diksha), , (A) electric force, , What is the magnitude and direction of, electric field below the plane?, (Diksha), , (A), , (D) LT A-3, , permittivity, the dimension of, , 20, , (B), , (A), , (B) LTA, , 94. If a = Surface charge density, & : electric, , and is equal to, , NC Assume T as tension in the string, Which, following options are correct?, , 2e volt/meter, , (C) o/e volt/meter, , Ans. (C) 9 x 10° N/C, , Ans. (A), , 15, , (A) 0 volt/meter, , (B) electric field internsity, , (C)pressure, , (5)2EP, LE0, , (D) electric charge, Ans. (B) electric field intensity, , C), (C), 11 x 10 C, , (B) T=5.55x 10 C, , 10 C, is oscillating, Apositively charged pendulumshown, x, , in the, in a uniform electric field as, figure below. What will happen to the time, period of pendulum when it is charged as, compared to when itwas uncharged?, , 2e0, , 95., , maximum torque on dipole is :, , charge, , (Diksha), , (A) R, , 87. A charged particle q is placed at the centre 0, of a cube of length L (ABCDEFGH). Another, at a distance L from, same, q is, 0. Then, the electric flux through ABCD is, , placed, , R, , 91. A cylinder of radius R and length L is place, in a uniform electric field E parallel to the, cylinder axis. The total flux for the surface of, the cylinder is given by:, , (A) Time period will increase, , (B) Time period will decrease, , (C) Time period will remain unchanged, (D) Time period will first increase, then, decrease, Ans. (A) Time, period will increase, 85. A sphere of 0.2 m, diameter bears, 1 microcoulomb, charge on it. The maximum, electric intensity at a, point due to the sphere, will be, , (A) 4/4TeL, , (B) zero, , (C)q/2teL, , (D) q/3teg L, , Ans. (B) zero, 88. Six charges,, , three, , positive, , following arrangements, possible for P, S, T and, , (B) The dipole will experience a force, towards right, (C) The dipole will experience a force, towards left, (D) The dipole will experience a force, , (B), , upwards, Ans. (C) The dipole will experience a force, , and, , of, , towards left., , (D) Zero, three, , negative of equal magnitude are to be, placed at the vertices of a regular hexagon, such the electric field at O, is double the, electric field when, one positive charg, only, of some, magnitude is plaçed at R. Which 0, , the, , (C)4x 10 Nm, Ans. (C) 4x 10° Nm, 96. In electric field lines in which an electric, dipole p is placed. Which of the following, statements is correct?, (Diksha), (A) The dipole will not experience any force, , Ans. (D) 1, , (A) 2RE, , (Diksha), , (A) 22x10- Nm, (B) 8x 10 Nm, (D) 4 x 10" Nm, , (), , (, , (C), , Two, equal and opposite charges 270 C are, placed at a distance of 1 cm forming a dipole, and are placed in an electric field 2 x 10`N/C,, , down, , to:, , 4.55 x 103 C, , Ans. (A)=11, 84., , (D),up, , 90. According to Gauss law, electric field on, infinitely long straight wire is proportional, , Ans. (C), , (C)4 18 x 10 C, D) T, , down, , (D), Ans. (A), , (A) =, , 0, , charges, , Urespectively?, , Ans., , (D) Zero, , 92. Two infinitely long parallel conducting, plates having surface charge densities +a, and-o respectively, are separated by a small, distance. The medium between the plates is, vacuum. If eg is the dielectric permittivity of, vacuum, then the electric field in the region, , between the plates:, , (Diksha), , 97. The ratio of electric field due to an electric, dipole on its axis and on the perpendicular, bisector of the dipole is:, (Diksha), (A) 1:2, (B) 2:1, (C) 1:4, (D)4:1, , Ans. (B) 2:1, 98. What will be the value of electric field at the

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VIDYA maKmarks, 16, , PHYSIcs | CLASS 12, (Diksha), , centre of the electric dipole?, (A) Zero, , to one, the electric field due, centre, the, at, charge, one chargee, Twice the electric field due to, , (8) Equal, , (C), , to, , at the centre, field due, (D) Half the value of electric, centre, the, at, charge, Ans., , Twice the electric field due to, at the centre., , (C), , one, , to, , charge, , (C), (D), , false, Assertion is true but Reason is, true, Assertion is false and Reason, , (D), , Electric field ines do, , not, , move, , rotatory motion., Reason : In a nonuniform electric field, a, dipole experiences a force as well as torque., , (CBSE SQP 2021), , on, , straight path, Ans. (B) Atraction between opposite charges, 100. Electric field required to keep a water drop, when, of mass m just to remain suspended(Diksha), , charged with 1 electron is:, , Ans., , (A) Both Assertion and Reason are true, , and Reason is the correct explanation of, Assertion, , Explanation:, , (A), , F, F, But, , (B)-Q/4, , (C)Q/4, , 91, 4E, , E E2, , A force F acts between the two spheres. If a, , third, sphere with charge Q is kept between, then it experiences a force in magnitude and, , Explanation : Gravitational force is the, , (A), (B), (C), (D), , (Diksha), , 8F towards +Q charge, 8F towards Q charge, Zero having no direction, 4F towards +Q charge, , Ans. (B) 8F towards-Q charge, 103. What is the SI unit of, , permittivity, , space?, , (C)CN m2, , Ans. (C) CN, , dominating force in nature and not coulomb's, torce. Gravitational torce is the weakest force., , Mistakes to Avoid, (Diksha), , (A) Weber, , Reason, , Also, Coulomb's force >> gravitational force., , of free, , Read the given statement carefully and compare it witn, the actual facts., , (B) Farad, , A Enhance your Answer, , (D) CN m2, , Give the clear reasons for, , m2, , Assertion-Reasoning Type 1Mark, , Ans., , 3. Assertion:, , depends on presence of all charges., 8. Assertion: Electric field at any point diverges, , Ans. (D) Assertion is false and Reason true, , positive charge and converges at a, negative charge., Reason: A charged particle is free to m o r e in, an electric field always m o v e along a n electric, from, , Explanation : Coulomb attraction exists, even when one body is charged, and the, other is uncharged., 5. Assertion: The, the, which 2 charges attract or repel, , property that, , force with, each, other, third, of, , Assertion, , and, , charges, , between any two bodies,, lost, but some loss of, , no, , charges,, force, , Reason is false, Ans. (C) Assertion is true but, on the, It, :, depends, Explanation, nature of, the charge, that it will m o v e in the direction, of electric field or opposite to it., , 9., , one, , at, , a, , other are not affected by the presence of a, , Reason:Force on any charge due to, , unaffected due to the presence, charges. This is the principle of, , bodies are charged through, , friction, there is a transfer of electric charge, from one body to another, but no creation or, destruction of charge., Reason This follows from conservation of, , electric charge., Ans. (A) Both Assertion and Reason are true, Reason is the correct explanation of Assertion, , and, , Explanation: Conservation of electric charge, states that the total charge of an isolated, remains, , unchanged with time., , are, , charge, , energy does, , shared, , is really, , occur, , f and, flux, , over, , the shown gaussion surface depends only on, , charges q' and q., , a, , number, , of other charge is the vector sum of all the, , forces on that charge due to other charges,, , time. The individual, , superposition of charges., 6. Assertion: When, , system, , Assertion The property that the force with, which two charges attract or repeal each, , third charge., , taken, , are, , a, , line of four, , Reason are true but, , 7. Assertion: Four point chargesq, q are as shown in the figure. The, , choosing a particular option, , When, , present., (D) Assertion is false and Reason true, , Explanation : Electric field at any point, , neutral., , Reason: In coulomb attraction two bodies, are positively charged., , of other, , force in the universe., , : Coulomb force is stronger than, the gravitational force., Ans. () Assertion is true but Reason is false, , direction as, , gaussion surface depends on all charges, , due to a, Explanation : Force on any charge, number of other charges is the vector sum, of all the forces on that charge due to other, , 2. Assertion: Coulomb force is the dominating, , Ans. (B)2/4, 102. Two spheres having charges +Q and Q is, kept at a certain distance from each other, , the law of conservation of charges. Energy IS, , also conserved, if we take in account of the, , Assertion, , FnetFi-F, , (D) Q/2, , Surrface, , Reason is NOT the correct explanation of, , (Diksha), , Gaession, , Reason : Electric filed at al points on the, , Ans. (B) Both, , The system of the three charges will be in, , 2, , 3, , Explanation : Charges are conserved by, , forces on that charge due to other charges,, taken one at a time., , (C) emg, Ans. (B) mg/e, 101. A charge '7 is placed at the centre of the, line joining of two equal +ve charge Q., equilibrium, ifq =:, , Ans. (A) Both Assertion and Reason are true and, Reason is the correct explanation of Assertion, , a, are not affected by the presence, charge., number, Reason: Force o n any charge due to aof all the, of other charge is the vector s u m, , (B) mg/e, (D) eg/g, , (A) g, , Reason:, Some of the energy is dissipated in, the form of heat, sparkling, etc., , between two bodies, one of them must be, , a dipole will have translatory as well as, , contraction, , 17, , Electric Charges And Fields, , loss of energy by heat, sparking etc., 4. Assertion : If there exists coulomb attraction, , 1. Assertion : In a non uniform electric field,, , and, , force, , between, , a r e true but, Assertion and Reason, (B) Both, Reason is not the correct explanation of, , Assertion, , length wise, it, 99. Electric field lines, (Diksha), hows, (A) Repulsion between same charges, (8) Attraction between opposite charges, relation, , below, are, true and, Assertion and Reason, (A) Both, Reason is the correct explanation of Assertion, , one, , contract, , (C) No, , a n s w e r to these questions, Select the correct, (C) and (D) a s given, from the codes (A), (B),, , taken one a time., Ans., , (B) Both Assertion and Reason are true but, Reason is NOT the correct explanation of, Assertion, , Explanation: Force on any charge due toa, number of other charge is the vector sum of, all the forces on that charge due to the other, taken one at a time. The individual, force are an affected to the presence of other, , charges,, , charges. This is the principle of superposition, , of charges., , Case/Source Based Type, 1. The electrostat, , 1 Mark, , process is used in inkjet, , printers where a nozzle finally sparys tiny, droplets, which are then given an electrostatic, , charge. The droplets are directed using pairs, of charged plates, and they form letters and, on paper. Colour inkjet printers, images, black, cyan, magenta and yellow jet., , use

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VIDYA maKmarks, , 18 PHYSIcs | CLASS 12, 2. Coulomb's law, , Coulomb's law is a quantitative statement, about the force between two point charges, When the linear size of charged bodies are, much smaller than the distance separatin, , (v), , force, , between, , two, , point, , charges and found that it varied inversely, , Now, Answer the following questions:, , () Which 10, , electrons are removed from a, , neutral metal, , sphere,, , the, , charge, , phere becomes:, , (A) 16 HC, (C) -32 HC, , on, , the, , (D)-16HC, , Explanation:, Since,, , = ne, =, , 10, , x, , 1.6, , x, , = 1.6 x 105, , 10-, , 16 x 10 C =16 4C, () Find the force between 2C and -1C separated, =, , by a distance 1 m in air (in Newton):, (A) 18 x 10N, , (B) 18 x 10° N, (C) 18 x 10 N, , (, , 10°N, , Ans., , (iv), , -18 x10°N, , centre ?, , TTEa, (D) None of these, , Ans. (A) 0, , Explanation : Due to symmetry all force, due to, , 3. Electrostatic spraying is a powder coating, method that involves the use of a spray gun, to apply the coating on a work piece surtace., In this, an electric charge is created on the, powder particles, which makes it cling on the, surface., This method is a fundamental concept of, the coulomb's law where by the electrical, forces of the two materials is what creates the, magnetic like attraction., , The benefits of the, methods are cost, environment friendly,, , electrostatic, spraying, effective method,, finished product is of, , and very effective method of, , Explanation: The standard unit of charge is, 1 coulomb is defined as the 1 N of, , coulomb., force applied on 1 unit of electric field., , (v), , charge Q, the effect of charge Q2 on Q, , Ans., , (C) from 1C to 4C, , (D) from 4C to, , Explanation: Since, the charge are unlike,, the force will be attractive. Thus, the force, directs from 1C to 4C., , 4. The electric lines of forces emerges from, , charge. Electric field lines is a path, straight, our curved in the electric field such that, tangent to it at any point gives the directon, of electric field intensity at that point. The, electric field lines of stationary charge don't, form closed loop. The field lines of uniform, , charges cancel each other at centre., , applied to static, Explanation: Coulomb isbetween, two, , (iv), , A, , point charges is proportional to the product, , (i) The coulomb law is, law, , -F2, , of 2 x 10 C is acted, upon by a, force of 0.1N. Determine the, distance to the, other charge of 4.5 x 10", C, both the charges, , are in vacuum., , 0.03, , Ans. (D) 0.09 m, , (B) 0.05, , (C) 0.07, , (D) 0.09, , Explanation : Since, F 4Te, 0.1= 9X10"x2x10x4.5x107, P9x9x 1010 x (1073, r, 9 x 10° x, (10), = 0.09 m, =, , any, , See, , the, , figure, , below, , and, , answer, , the, , question., , the square of the distance between them., , F+ Fa =0, , charge, , It states that force, , electric field are parallel and equidistant., , (), , of the charges and inversely proportional to, , charges is given by F and F2, , Now,, , a, , positive charge and ends at the negative, , Ans. (A) Electrostatics, , Explanation: Force on each other w.rt., , 1C, , Ans. (C) from 1C to 4C, , () Coulomb's law is employed in, (A) Electrostatics, (B) Magnetostatics, , charges., , charges 1C and 4C exists in air. What is, , (A) away from 1C, (B) away from 4C, , (C) Electromagnetics (D) Maxwell theory, , and, , Two, , the direction of force?, , Answer the following question:, , F2 are not equal, (B) F =-Fa, , (A), (B)9, , Ttega, , a, , (D) F, , (D) Hyperbola, , charges of charge q are situated at the, corners of the 12 sided, polygon of side a., What is the net force on the, charge Q at the, , (C) 9 0, , Ans. (C) charge, , 9.8, , = 9.81 x 1 0, , good quality, , Coulomb is the unit of which quantity ?, (A) field strength, , (B) permettivity, (C) charge, , =, , =, , 12, , (A) 0, , For, , v), , painting, , (B)F-F2, (C)F F2 0, , What is the locus of an electron projected, perpendicular to a uniform electric field ?, (A) Circle, (B) Parabola, (D)Hyperbola, , (B) Charge, (D) Force, , (A)F=F, , -2x1x9x10, (C) Ellipse, , (A) Field strength, , willbe,, , F = 12, 4Teor, , x, , get, r = 0.3m, , repulsion between, , (ii), , 103, , charges., , Ans. (B) Charge, (i) As per Coulomb's law, the force of attraction, or, two point charges is, directly proportional to the:, (A) sum of the magnitude of charges, (B) square of the distance between them, ()product of the magnitude of charges, (D) cube of the distance, Ans. (B) square of the distance between them, , Explanation, (ii), , mg =, , x, , On calculating r by subsituting charges we, , (C) Permittivity, , +F2 = 0 and Fi = -F2, , (D) force, 10, , and acted along the line joining the two, , Coulomb is the unit of which quantity?, , Explanation: As the force of two charges, w.rt each other is given by Fj and F. Thus, F, , (C) 0.3, , Explanation:, , Explanation : F x, , (D)-18 x 10°N, x, , Ans., , product of the magnitude of the two charges, , (B) 32 uC, , Ans. (A) 16 uC, , Ans. (B) -18, , as the square of the distance between the, charges and was directly proportional to the, , balls, , between the balls if the lower, ball is restrained from moving., (A) 0.5, (B) 0.4, (D) 0.2, (C)0.3, , bodies are treated as point charges. Coulomb, the, , Two small diameter 10gm dielectric, can slide freely on a vertical channel., Each, carry a negative charge of 1uC. Find the, , separation, , them, the size may be ignored and the charged, measured, , 19, , Electric Charges And Fields, , Ans., , an, , implication of which, Conductor, , (A) ampere law, , (B) gauss law, , (C) biot Savart law, , (D)lenz law, , (B) gauss law, , Explanation: The coulomb law can be, formulated from the gauss's law, using the, , Whether the electric field lines shown, , divergence theorem. Thus, it is an implication, , properly represented?, (B), (A) yes, , of Gauss's law., , (C) can't decide, , (ii) For a charge q, the effect of charge ga on q1, willbe:, (A) F, , = Fa, , (C)F =F=0, , Ans. (B) F =-F2, , (B)F =-F2, (D)F, , F2, , are, , no, , (D) None of these, , Ans. (B) no, Explanation: The field of lines in figure, can't shown electrostatic field lines, lines are not normal to surface., , as, , these

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VIDYA MaKmarks, 20 PHYSIcs, , CLASS 12, , (B) they, , () Does the figure represent the possible, , are, , Lr, , to the surface of, , a, , h, , charged, , conductor, , electrostatic field lines?, g'<q, , (C) they alwasy, (D), , forms closed, , and, they are parallel, uniform electric field., , in, , of, , region, forms closed loops, (C) they alwasy, Explanation: Electric field lines do, not, It start from, form a closed loops., (+)ve, on (-)ve, charge., charge and terminate, is placed in uniforn, electric, dipole, When, 5., , (B), , (A) yes, , (C) partially correct (D) can't decide, , Explanation : It represent electrostatic feld, , and torque t on the dipole are:, (B) F+0,t =0, , (C) F=0, Tt#0, , (D) F+0,t =0, , rise to some torque on the dipole. Since, net, force on electric dipole is uniform electric, , Ans. (C) F=0, T «0, , (B) ircular outwords, 2/ sin, , F-gE, ()The dipole moment of a dipole in a uniform, external field E is B. Then, the torque, , lines due to two positive charges. The, , acting on dipole is :, , magnitudes, E Ep and Ec of the electric, fields at point A, B and C respectively are, , (A) T= pxE, , (B)T=2(p+E), , (C)r=p.E, , (D) T=p+E, , related as :, , Ans. (A) T=pxE, , (i), (A) EAE Ec, (C) E Eg > Ec, Ans. (A) EA Eg> Ec, , (), , An electric, dipole consists of two opposite, charges, each of magnitude 1.0 uC separated, , (B) Ep>E > Ec, , by a distance of 2.0 cm. This dipole is placed, in an extemal field of, , (D) E>Ep=Ec, , torqueon dipole is:, , Explanation: As E is inside the electric, field lines, Eg is near the electric field line, and, Ecis in the region, where are no electric field, lines., Which of the, following is false about electric, lines of force?, , (A) they always starts from (+)ve, charge and, terminate on (-}ve charge., , Then itis minimum at 0 =0° and 180., , (A) F=0,t =0, , E, , 10° N/C. The maximum, , (A) 0.2 x 10 Nm, , (B), , 1x, Nm, (C) 2 x 103 Nm, , 10, , (D) 04 x 10-3 Nm, Ans. (C) 2 x, 10 Nm, , Explanation:, , t=, , p xE, , 2qa x E, =1x 10*, , =2, , x, , 10, , x 2x 104x 10, , Nm, , (A), (B), (C), (D), , Explanation : Since, t =pË sine., , in uniform electric field is zero. However, these forces are not collinar, so they, , dipole against the torque acting on it., , (iv) The figure below shows the electric field, , (D) Both (A) and (C), Ans. (D) Both (A) and (C), , other and hence net torce on electric dipole, , (A) radially outwords, , Explanation: As electric field lines appears, to emerges out of the positive charge., , (C) 180, , in a uniform electric field, the net force F, , However, some work is done in rotating the, , (C) radially inwords, (D) parallel straight lines, Ans. (A) radially outwords, , direction of, dipole makes a n angle with the, to, the field. Assuming that PE. of the dipole, and PE. of, be zero, when 0 = 90°, the torque, the dipole will be respectively are, , (iv) When an electric dipole is hold at an angle, , the electric dipole in uniform electric field., , An electric dipole, placed in, an electric field of intensity E. The dipole, the, a position such that the axis of, of moment p is, , acquires, , (B))90°, , equal and opposite forces, which cancel each, , field is zero, so no work is done in moving, , because the field lines emerges from the + ve, charge and repel each other, (ii) Electric lines of force about a positive point, charge are:, , (v), , (A), , electric field, its two charges experience, , give, , Ans. (A) yes, , ()Torque on a dipole in uniform electric field, is minimum when 6 is equal to :, , loops, , equaly spaced, , Ans., N, , 21, , Electric Charges And Flelds, , Explanation : Net force acting on dipole is, zero. But torque acting on it is not zero until, , it get aligned in the direction of electric field., , Ans., , pE sin 0,-pE cos 0, , pE sin , -2p E, pE sin 0, 2p E, , cos, , cos, , pE, , cos, , 9, , 6,-pE sin, , (A) pE sin 6, - pE cos, , Explanation : pEsin 0,-pE cos, , TpxE=pEsin 8, PE. =, , (cos 90°-cos 6), , - T cos 0, , -pE cos 0