Electrostatics MCQs + Memo
.pdf
School
Nelson High School**We aren't endorsed by this school
Course
PHYSICS 12 ADD34M
Subject
Physics
Date
Dec 31, 2024
Pages
62
Uploaded by thatokhoza06479650
CONCEPT 1' Two charges of + 2 nC and - 2 nC are located on a straight line. S and T are two points that lie on the same straight line as shown in the diagram below. Which ONE of the following correctly represents the directions of the RESULTANT electric fields at S and at T? DIRECTION OF THE RESULTANT ELECTRIC FIELD DIRECTION OF THE RESULTANT ELECTRIC FIELD AT POINT S AT POINT T A Right Left B Left Left C Right Right D Left Right Two charges, + Q and — Q, are placed a distance d from a negative charge - g. The charges. + Q and - Q, are located along lines that are perpendicular to each other as shown in the diagram below. +Q, d ,------- =4 .....-d----._ Q Which ONE of the following arrows CORRECTLY shows the direction of the net force acting on charge — q due to the presence of charges + Q and - Q? [N
Two identical light graphite-coated spheres, Py and P;, are suspended using identical thin insulated threads. Py is charged, but Pz is neutral. The spheres are then brought Into contact with each other, as shown In diagram I Thereafter the spheres assume the positions, as shown in diagram I1 Diagram I Diagram 11 P' ‘ ’ ,Pz Which ONE of the following statements conceming the charges on the spheres possibly explains why the spheres move apart after touching, as shown in diagram II? SIGN OF SIGN OF MAGNITUDE OF CHARGE ON P4 CHARGE ON P2 | CHARGES ON P14+ AND P2 A + + Unequal B - Unequal C + - Equal D + K Equal Three charged spheres X, Y and Z, supported by insulating threads of equal length, hang from a beam, as shown in the diagram below. Sphere X Is negatively charged. Sphere X attracts sphere Y, but repels sphere Z. L 1 @ & © x Z Y Which ONE of the following conclusions is CORRECT? A Sphere Y is positively charged and sphere Z is negatively charged. B Sphere Y is positively charged and sphere Z is positively charged. C Sphere Y is negatively charged and sphere Z is negatively charged. D Sphere Y Is negatively charged and sphere Z Is positively charged.
1. A For electric fields PONI (positive out negative in) and due to the charges having the same magnitude the one furthest away will be the weakest one. 2.C The -Q charge will push the -q charge to the left and the +Q charge will pull the -q charge upward. Like charges will repel and unlike charges will attract.
3D In diagram 2 the spheres are repelling each other, therefore either both spheres are positive or both spheres are negative. The __ Q1+ Q7 formulais Qyew = , because it is divided by 2, the magnitude of the charge on each sphere would have to be equal. 4. A Like charges will repel and unlike will attract. Sphere X is negatively charged and attracts sphere Y meaning sphere Y will have to be positively charged. Sphere X is negatively charged and repels sphere Z therefore sphere Z will have to be negatively charged as well.
5-Two identical metal spheres, P and R, on insulated stands, carry different 6 charges. The spheres are brought into contact and then separated again. Two spheres, A and B, have charges of +1 C and +2 C respectively. They are brought into contact with each other and then moved to their original positions. The amount of charge transferred is ... 05CfromBto A If the charge on sphere R AFTER the separation is g, the charge on sphere P after the separation is ... 05CfromAtoB. A B 15CfromBtoA. Zer0. o O o » B 1,5CfromAto B. C lessthanq. D greater than q.
= Two small, identical oppositely charged spheres suspended from light Inextensible strings, are held In fixed positions and prevented from touching. Refer to the diagram below. Which ONE of the following statements best describes the behaviour of the spheres when they are released? > They will move towards each other, touch each other momentarily and then separate. They will move towards each other, touch each other momentarily and remain in contact. They will remain at their original positions and then vibrate, They move away from each other momentarily and then move towards each other. o0 m 8. The electric field pattem between two charged spheres, A and B, is shown EX = Which ONE of the following statements regarding the charge on spheres A and B is CORRECT? A Sphere A is negatively charged, and sphere B s positively charged. B Sphere A is positively charged, and sphere B is negatively charged. C Spheres A and B are both positively charged D Spheres A and B are both negatively charged.
5.A Qnew = magnitude of the charge on each sphere would have to be equal. Q1+ Q2 , because it is divided by 2, the 6.B Qnew = 21_;—0_2 Qnew = 1;_2 Qnew = 1,5C Sphere B will have to gain 0,5 to getto 1,5 and sphere A will have to lose 0,5 to get to 1,5, therefore it is from A to B.
7. A 8. A Unlike charges will attract. After they touch | PONI (positive out negative in) each other the charge will be transferred and both spheres will then be both negative or positive and will then repel.
9. 10. Which one of the following graphs best represents the relationship between the magnitude of the electric field (E) and the charge (Q) at a distance r from the charge? A ET B Which ONE of the following combinations is CORRECT regarding the [ L properties of electric field lines? \ Direction Strength of field 75- fi - Positive to ngggtive Strorpest wt?ere the lines are the mostc{en_s_e_ ¢ E‘T 3 B Negative to positive | Weakest where the lines are the least dense E C North to south Strongest where the lines are the most dense D North to south Weakest where the lines are the least dense
10, Two IDENTICAL SPHERES X and Y, with a charge of -Q and -2Q are suspended from the same Insulated point as shown In the diagram below. (The diagram is not drawn to scale.) The spheres are then allowed to SMDg lreely until mey come to rast on thelr own. How will the magnitudes of the angies ganda compare to each other once the spheres come 1o thelr positions of rest? lg\ore the effect of the masses of the strings and the spheres. 6<a 6>a B=-q o o o » 6=a=0° 12 P, Q and R are three charged spheres. When P and Q are brought near each other, they experience an attractive force. When Q and R are brought near each other, they experience a repulsive force. Which ONE of the following is TRUE? A P and R have charges with the same sign. B P and R have charges with opposite signs. C P, Q and R have charges with the same sign. D P, Q and R have equal charges. .
9.C As the magnitude of the charge increases the electric field will increase in the same proportion. 10. A PONI (positive out negative in) therefore, from the positive in to the negative (from positive to negative). The strength of an electric field is strongest where the lines are most dense. Electric field strength is greatest where the lines are closest together and weakest where lines are furthest apart.
11.C Newtons third law. Force is equal but opposite in direction. If force is equal the angles opposite it will be equal. 12.B Like charges will repel and unlike will attract. P and Q experience an attractive force which means the charges will have opposite signs. And Q and R experience a repulsive force which means no matter which one is regarded as positive or negative charges P and R will have to have opposite signs.
13 Sphere A, with a charge of +Q, and sphere B, with a charge ol +2Q, are . suspended from the same insulated point as shown in the diagram below. (The diagram is not drawn to scale.) The spheres are allowed to move freely until they come 1o rest on their own, Howw:lhevalu@sofmeanglesaandboonmarewcadmdhermm spheres come fo rest? A g=8 B a<p C a>B D a=B=0 14. Two small, oppositely charged spheres on an insulated surface are held a distance r aparl as shown in the diagram. r sa f L+ T b s s T When the spheres are released simultaneously, they roll towards each other due to the electrostatic force of attraction. Which ONE of the following graphs represents the magnitude of the force experienced by each sphere as a function of the distance r between their centres? A B Vo N
15 Point charges Qq, Q; and Q4 are arranged at the corners of a right-angled 16 triangle, as shown in the diagram below. The charges on Qq, Q2 and Qs are unknown. The distance between Qq and Q; is r. The distance between Qz and Q; _ ) _ _ ) is also r. Charge Qg experiences a Tesultant electrostatic force to the WEST. Which graph represents the relationship between the magnitude of the electrostatic force, FE' between two charged spheres and the distance, r, between the centres of 2 N the spheres? AV r 'a" \\\! w+ E ’ ’ “\ A B g 45' . s A — F Fe Q [ C Which of the following combinations of charges could be possible for charges Q, e (e Q; and Q37 A B C NEGATIVE D NEGATIVE NEGATIVE POSITIVE NEGATIVE POSITIVE C Fe D Fe Q4 Q; Qs NEGATIVE POSITIVE POSITIVE POSITIVE POSITIVE POSITIVE A
13. A 14.D As the distance between them decreases the force will increase and according to the K : : formula F = —%Q—Z, distance is squared meaning that the graph would have to be parabolic.
15. A For the charge Qs to experience a resultant electrostatic force to the West Q, would have to push Qs away and would therefore have the same charge, Q; would have to pull Qs and would therefore have different charges. 16.D As the distance between them decreases the force will increase and according to the K : : formula F = %Q—z, distance is squared meaning that the graph would have to be parabolic.
17. 18. _ Consider the charged particles in diagrams 1 - 4 below. A small test charge +q is placed exactly half way between two identical negatively charges, X and Y, each with a charge + Q, as shown below. T @@ - 2 @+-0 +Q +q +Q * = e 3 O®- X d d Y 4 @@ The charges have the same magnitude. In which case does the electric field at the dot (*) have the LARGEST magnitude? The test charge +q will 1 A remain where it is B 2 B move towards X c 5 C move towards Y D move vertically downwards D 4
19. Two charged spheres V and W are located on a straight line. X, Y and Z are three points on the same straight line. The positions of points X, Y and Z are as indicated and the direction of the NET electric field at points X, Y and Z is shown in the diagram below. A < i i I-< N v Which ONE of the following combinations represent the charges on each of the spheres V and W? 20 The electric field pattern between two charges Q, and Qz is shown below. 2 O=0 N/ Which ONE of the following statements regarding the charge Qy and Q2 is Charge of V Charge of W CORRECT? - A Positive Positive [ Chargea_ Charge Q2 | B Neutral Positive re Negat;e_ Negative —] C Negative Negative Fé Positive Negcfttive ] D Positive Negative E ':2:3’: :::::: |
17. A Like charges will repel and unlike will attract. Both charges X and Y will push the test charge away, however since charges X and Y are of the same magnitude and they are the same distance away from the test charge the forces will be equal, making the net force ON. 18.B For electric fields PONI (positive out negative in). For number 2 the positive charge will push the dot to the right and the negative charge will pull it to the right, therefore the electric field will have the largest magnitude.
19. A For electric fields PONI (positive out negative in). For point Z to experience a net electric field to the right charge W would have to push it out to the right, this means charge W would have to be positive. For point Y to experience a net electric field to the right charge V would have to push it out to the right, this means charge V would have to be positive as well. 20.B For electric fields PONI (positive out negative in).
Zl. 22. Which ONE of the diagrams below shows the correct electric field pattern between two equal, but opposite charges? Which ONE of the diagrams beiow is NOT the comect slectric fieid pattem due o an jsolated point charge? e e %
23. Two small identical objects, each with a net charge of +Q, are placed next to each other in a vacuum tube. They move apart. ol G o Which ONE of the following statements is CORRECT? The electrostatic force will ... A decrease at constant rate. B decrease exponentially. C stay the same. D increase at constant rate. 24, A positive charge is placed at rest at the center of a region of space in which there is a uniform, three-dimensional electric field. (A uniform field is one where field strength and direction are the same at all points within the field.) When the positive charge is released from rest in this uniform electric field, what will its subsequent motion be? The charge will ... A move at a constant speed. B move at a constant velocity. C remain at rest in its initial position. D move at a constant acceleration.
21.D For electric fields PONI (positive out negative in). 22.C The electric field lines are not complete, it should look like charge A.
23.B ) : __ kQ40Q, According to the equation F = —5 as the distance increases the electrostatic force experienced by two point charges will decrease exponentially (because r is squared). 24.D The charge will move with a force applies on it, so therefore it must have acceleration.
25. A leamer has represented the electric field £at points A, B, C and D due to a positive point charge Q as shown below. C E‘ \‘A ./'E O g, 9B ‘\' Which ONE is the correct representation? D 26. The sketch below shows a negative and a positive point charge. The magnitude of the positive charge is greater than that of the negative charge. Midpoint O Where on the line that passes through the charges is the total electric field zero? A To the right of the positive charge. B To the left of the negative charge. C Between the charges, to the left of the midpoint. D Between the charges, to the right of the midpoint.
27. The electric field pattern of two small charged objects are shown below. Which one of the following diagrams correctly shows the force experienced by a positive test charge placed at a point in the field? F Q) %{% 28 " In the diagram below, Q is a negatively charged object. (@) X The direction of the electric field line at Point X is: A to the left B up C totheright D down
2o.C 26.B For electric fields PONI (positive out negative in). The negative charge will pull in while the stronger positive charge will push out leaving the net electric field to be 0.
27. A For electric fields PONI (positive out negative in). The positive charge will push it to the right and the negative charge will pull it to the right. This will result in the net electric field acting to the right. 28. A For electric fields PONI (positive out negative in). The negatively charged object will pull into the left.
28, A small negative point charge (q) is situated halfway between two identical spheres, P and Q, carrying IDENTICAL charges, as shown below. Sphere P exerts an electrostatic force of magnitude F on sphere Q. What is the magnitude of the net electrostatic force experienced by the point charge? A Zero 1 B ~F 2 C F D 2F
29. A The force of P on q and the force of Q and q will be equal but will act in different directions, therefore the net electrostatic force acting on g will be ON. CALCULATION
Two identical spheres. R and S. on insulated stands, carrying charges of +q and -q respectively. are placed a distance apart. Sphere R exerts an electrostatic force of magnitude F on sphere S. The two spheres are now brought into contact and returned to their original positions. The magnitude of the electrostatic force that sphere R exerts on sphere S Is now ... A Zero s © 2 cC F 2. Two small, identical positively charged spheres P and Q on insulated stands are placed a distance d apart as shown below. The magnitude of the force exerted by Qon P is F. - a S ” " - If the distance is now changed to 'z d, the new force between the spheres is ... A W%F B »%F C 2F D 4F
3 . Two identical charges Q1 and Q2 are placed a distance r apart. The charges . : 4 I i d a dist experience an electrostatic force F. The electrostatic force between two point charges that are place ance r apart in a vacuum is F. +Q . ¢Qx The distance between the charges is changed and the electrostatic force r * When the distance is ..., then the force changes to 4F. Which ONE of the between them changes to 16 F. What is the new distance between the point following changes in r will produce a force 4F? charges in terms of r? Original distance New distance A B8r A r 3r , B 1, B r -r " - c . ;r C 4r D r r D 1 r 4
1.A Qnew = % Qnew = 3+(2_3) Qnew =0C Since both spheres now have a charge of 0 C The electrostatic force that R exerts on S will be O N.
3. Three small identical spheres, A, B and C is charged as shown in the diagram. The distance between sphere B and C is x. +16 pC -4 uC +4 uC LA B C ® ® < - X For sphere B to experience no resultant electrostatic force, the distance between A and B must be ... A Vax. B Yax C 2x. D 4x " The electric field experienced by point char ge P due fo the presence of point charge R at a distance r from P, is equal to E. O O, If the distance between P and R is increased to ic fi experienced by P will be ... 2r, the electric field A 4E. B 2E. C ¥E D VE.
A positive test charge q is held at Y between two positive charges +Q and +3Q as shown below. +Q q +3Q O« " »oe 2r O X Y Z When released, q will ... A B C D remain at Y. move towards X. move towards Z. move vertically downwards. 8. Two charged spheres on insulating stands carrying charges Q and Q; are kept a distance r apart. Each sphere exerts an electrostatic force of magnitude F on the other. The distance between the spheres is now DOUBLED and the charge on one sphere is HALVED. The magnitude of the new electrostatic force on a sphere N A B (2) oMaeamomM M
5.C Let the distance between A and B equal toy kQ1Q> — r2 kQ1Q> 2 (9%x10%)(16)(4) _ (9%x10°)(4)(4) y?2 x2 y = 2x
7.C Plug in random values for Q and R and your answer will indicate C kQ1Q F = o o 3) (2r)? 1 F = —2_
9. Two identical charged spheres are kept apart at a distance d. The force exerted on one charge by the other is F. What is the new force when the charge on one sphere is DOUBLED? 10. Two charged spheres. A and B, are placed on insulated stands a distance r apart, as shown below. The magnitude of the electrostatic force between them is F. - g : o S A 2F B F The spheres are allowed to touch each other and are then moved back C ] to their original positions. The magnitude of the electrostatic force in EF terms of F will now be ... 1 A B8F D -—F 4 B F 1 5 zF 1 D 'F
11. Point P is situated a distance r from point charge q as shown below. The electri field at point P due to point charge g is found to be E. o« L »0 P +q The electric field at point @ which is on a distance %r from point charge g will be: 1 §E 1 ~ 3 3E 9E 12. Two point charges are a distance r apart and are positioned as shown in the diagram below. An electrostatic force of magnitude F exists between the two charges. « r —> ........e e =01 +Q The distance between the two charges is reduced to %r . The new force between the charges is ... A F B 3F C SF 1 D -9F
10.D Before Contact F =@ r F=— 7-2 Charge on new Sphere Q:+Q Qnew = 12 2 —4+2 Qnew = > Qnew =-1C After Contact F - lezQZ T o (1)21) @ 1 P = =
13. 14. The centres of two identical metallic spheres, each carrying a charge Q, are a distance r apart. Which ONE of the following pairs of changes (that are made The number of excess electrons which will cause a charge of -8uC on a | simultaneously) will double the electrostatic force that one charged sphere exerts sphere, is equal to: on the other? A Sx108 Distance between centres | Magnitude of charges B 5x 10" of spheres C 5x 10" A | Decrease distance to_”_ Double the charge on D 5x 10-14 : V2 each sphere B | Decrease distance to _* Reduce charge on each V7 sphere to € C | Decrease distance to Reduce the charge on : one sphere to 2 D | Decrease distance to * Double the charge on 2 each sphere
15. Two small identical metal spheres, on insulated stands carmy charges -q and +3¢ respectively When the centres of the spheres are a distance d apant, the spheras exert an elecirostatic force of magnitude F on each other - — d e The spheres are now made to touch and are brought back o the same positions as befora The magnitude of the electrostatic force which the spheres now exert on each other, in terms of F, is: A 1r V4 B 3F ¢ s K] 16. A point charge exerts a force of magnitude F on another point charge. One of the charges is changed to one third and the distance between the charges is doubled. What is the new electrostatic force in terms of F? A w|m Rl 3 ‘I%
13.B 8uC = 8x10~°C 8x10° 1,6x10—1° n = 5x1013 kQ.Q r 1 F_2
15.C Before Contact F — lezQZ T F — (1)(3) re Charge on new Sphere Q1+Q Qnew = 12 2 —-1+3 Qnew = T Qnew = 1C After Contact F — lezQZ T F — (1)21) T F=— T 16. B kQ1Q F =k F=-= _ kQ41Q F=ra2 3 b= (21)2 3) 1 F= 12712
17 Three identical conducting spheres A, B and C are placed on insulated wooden stands. Spheres A and B carry equal charges. They are separated by a distance d and exert a force with magnitude F on each other, as shown in the sketch below. r—() —r ! d The third sphere C, which is uncharged, touches A, then B, and is then removed. If the distance between the spheres remains the same, then the magnitude of the electrostatic force exerted on sphere B is now: >l I A F 2 F B 3 3F Y F D_ 16 18. Three charged spheres, P, Q and R are placed as shown below. Q is POSITIVELY charged. - Q R e . d i Spheres Q and R are a distance d from each other and carry charges of +g and —g respectively. The charge on sphere P is NINE times greater than that on sphere Q. Which ONE of the following is correct for the charge on sphere P and the distance x between P and Q so that charge Q remains at REST? charge distance x A positive 45d B positive 3d C negative 45d D negative 3d
19. The electrostatic force that one point charge exerts on the other point charge must be increased by a factor of four by changing the distance between them. The distance between the two point charges must be... A increased by a factor of 2. B increased by a factor of 4. C decreased by a factor of 4. D decreased by a factor of 2. 20 The magnitude of the electric field is E at point M close to the charged sphere. T X " P M N 2x Which ONE of the following is the CORRECT magnitude of the electric field at point N, which is twice as far from the sphere as point M (as shown in the diagram above)? A 1l 2 B 2E 1 c :E
LY IR # 18.D kQ1Q2 _ kQ10Q7 r2 = 2 (V1) _ (1)) 2~ x2 i 9 d2 x* = G* ' Sphere P would have to be negative to attract sphere Q allowing it to remain at rest.
21, Two identical conducting spheres M and N carry charges of +12, 8 x 10-'% C and -12,8 x 109 C, respectively. The spheres are allowed to touch. How many electrons does M gain when the spheres touch? A 2 B 4 C 6 D 8 22, Two identical metal spheres X and Y, on isolated stands, have charges of +6 nC and -2 nC respectively. Y is brought into contact with X. Y is then placed in its original position again. +6 nC -2nC The final charge on each sphere is: X Y A 0nC 0nC B 3nC -1 nC C 2nC 2nC D 4nC 4nC
Two identical charges Q, and Q; are placed a distance r apart. The charges SO S SS— - Two positive charges, +Q and +2Q, are placed at point X and point Y - mm— respectively as shown in the diagram below. A POSITIVE charge q Is kept o e al rest between points X and Y, +Q q +2Q e o Xe i T / — : r :: > " PR, r Which ONE of the following combinations will result in an electrostatic force of 16F [ ' between the charges? ' Charge Q; Distance r When q is released, q will ... A 12 Qz 2r A stay al rest. - - i i P move towards X. c 2Q, ver C move towards Y. D 8 Q2 2r D imove vertically downwards.
21.D n=2 Je 12,8x10°1° n —_— 1,6x10~19 n=2~8 22.C Q1+Q Qnew = 12 2 -24+6 Qnew - > Qnew = 2 nC
kQ,0Q; — ey GN? 4 1.0 7! 16 re 24 5 C Right is taken as positive Frq = % Fyq = kilez Frq = riz Frq = (272*)2 Fig=— Feg = # Fret = .riz L3 # Fret = rizN Therefore, g will move to the right (towards Y)
25. Two small metal spheres, X and Y, on isolated stands carry charges of +2 nC and -6 nC respeclively. Sphere X experiences a force F due to the charge on sphere Y. The spheres are brought into contact with each other and are placed back in their original positions. The magnitude of the electrostatic force that sphere X now experiences, is... i 5 3 B 3F C 6F D 12F 26. Three charged spheres are placed horizontally along a shiaight ine. Spheres X and Y have identical charges of +Q. ‘What charge on sphere Z will result in a net force of 0 N on sphere Y7 OB OMNO -4Q +40Q ©eee I
2 8 Two small objects P and R carry charges +Q and +Q respactively. They 2 7 L . exert a force ; F on each other. Two small ocbjects, each with a net charge of +Q, exert a force of P R magnitude F on each other. @ @ F L B < : > R is now charged to +6 Q as shown in the diagram. In the P R One of the objects is replaced with another with a charge of +4Q. process the distance between the objects is doubled. The force that the one charge now exerls on the other charge is: If the distance between P and R remains the same, what is the force on P? A%F A 3F B 2F - C 4F 5 D F - -
25. A Before Contact F pee lezQZ : i B (2)26) | & Charge on new Sphere Q1+Q2 Qnew = 1_2' —6+2 Qnew = > Qpew = —2nC After Contact F e lezQZ ' F = (2)22) r 26.D F,,, would have to act to the left and would therefore make charge Z positive. Fy+FE,=0 kQ12Q2 + kQ12Q2 - O T r LW , , W@, _ (0.04)2 +( (0.02)2) - 2 =025 7 =1 +
27.D Before change F - kQ12Q2 - 1 e~ After Change __ kQq0Q F = 0 F = (4)(1) (2r)? F== r2 28.B Before change After Change F - kQ1ZQz - F = (6).21) 1 6 F = 1—2
29. When two identical metal spheres F and G are brought in to contact and then separated, it is found that the charge on each sphere is now -5 nC. Which ONE of the following combinations is CORRECT regarding the original charges on the spheres BEFORE they made contact? SPHERE F(nC) SPHERE G (nC) A - +25 - -15 - B -7 -3 C -5 neutral D -7 +2 30 Two identical isclated spheres P and Q have charges of +8 nC and -8 nC * respectively. A third identical sphere R is initially uncharged (neutral). Sphere R is moved and touches sphere P. Sphere R is now moved so that it touches Q after which the two spheres are separated again. What is the final charge on sphere R? P Q Qe=+8nC Qo=-8nC o Qg=0nC A +4nC. B -4 nC. C +2nC. D -2nC.
31. D i ol . M SOV O RTINS S GRS 1D SNOSMY The magnitude of the electrostatic force on a charge Q, due to another charge charge Q2 is F. The distance between charges Q¢ and Qz is r. One of the s h ot illheut o = the dist St charges is oubled 1 e dislance bebvesn the chames is hatved tthe :'F. Both charges are now doubled without changing the distance between The magnitude of the electrostatic force that Q2 now exerts on Q1 willbe: | The magnitude of the new electrostatic force on Q, will be: A iF A E B 2 B F B 2F Cc 4F e - D &F
29.B Q1+0Q Qnew = % -7+(=3) Qnew = > Qnew = —=5nC 30.D Qnew = % Qnew = 9;—8' Qnew = 4 nC Qnew = QI;QZ Qnew = # Qnew = —2nC
31.D Before change F — kQ12Q2 r 1 F = 1—2 After Change __ kQ10Q2 F — 7'_2 2 51)? 2 F = fi . F = - 32.C Before change After Change F — kQ1zQz . F = (2)22) . 4 =