gujcet capacitors

CAPACITANCE

1. The units of capacitance are equivalent to:

A. J/CB. V/CC. J2/CD. C/JE. C2/J

2. A farad is the same as a:

A. J/VB. V/JC. C/VD. V/CE. N/C

3. A capacitor C has a charge Q. The actual charges on its plates are:

A. Q, QB. Q/2, Q/2C. Q, QD. Q/2, Q/2E. Q, 0

4. Each plate of a capacitor stores a charge of magnitude 1mC when a 100-V potential dierenceis applied. The capacitance is:

A. 5FB. 10FC. 50FD. 100FE. none of these

5. To charge a 1-F capacitor with 2C requires a potential dierence of:A. 2VB. 0.2VC. 5VD. 0.5VE. none of these

364 Chapter 25: CAPACITANCE

MEDIIT

6. The capacitance of a parallel-plate capacitor with plate area A and plate separation d is givenby:

A. 60d/AB. 60d/2AC. 60A/dD. 60A/2dE. Ad/60

7. The capacitance of a parallel-plate capacitor is:

A. proportional to the plate areaB. proportional to the charge storedC. independent of any material inserted between the platesD. proportional to the potential dierence of the platesE. proportional to the plate separation

8. The plate areas and plate separations of five parallel plate capacitors are

capacitor 1: area A0, separation d0capacitor 2: area 2A0, separation 2d0capacitor 3: area 2A0, separation d0/2capacitor 4: area A0/2, separation 2d0capacitor 5: area A0, separation d0/2

Rank these according to their capacitances, least to greatest.

A. 1, 2, 3, 4, 5B. 5, 4, 3, 2, 1C. 5, 3 and 4 tie, then 1, 2D. 4, 1 and 2 tie, then 5, 3E. 3, 5, 1 and 2 tie, 1, 4

9. The capacitance of a parallel-plate capacitor can be increased by:

A. increasing the chargeB. decreasing the chargeC. increasing the plate separationD. decreasing the plate separationE. decreasing the plate area

10. If both the plate area and the plate separation of a parallel-plate capacitor are doubled, thecapacitance is:

A. doubledB. halvedC. unchangedD. tripledE. quadrupled

Chapter 25: CAPACITANCE 365

11. If the plate area of an isolated charged parallel-plate capacitor is doubled:

A. the electric field is doubledB. the potential dierence is halvedC. the charge on each plate is halvedD. the surface charge density on each plate is doubledE. none of the above

12. If the plate separation of an isolated charged parallel-plate capacitor is doubled:

A. the electric field is doubledB. the potential dierence is halvedC. the charge on each plate is halvedD. the surface charge density on each plate is doubledE. none of the above

13. Pulling the plates of an isolated charged capacitor apart:

A. increases the capacitanceB. increases the potential dierenceC. does not aect the potential dierenceD. decreases the potential dierenceE. does not aect the capacitance

14. If the charge on a parallel-plate capacitor is doubled:

A. the capacitance is halvedB. the capacitance is doubledC. the electric field is halvedD. the electric field is doubledE. the surface charge density is not changed on either plate

15. A parallel-plate capacitor has a plate area of 0.2m2 and a plate separation of 0.1mm. Toobtain an electric field of 2.0 106V/m between the plates, the magnitude of the charge oneach plate should be:

A. 8.9 107 CB. 1.8 106 CC. 3.5 106 CD. 7.1 106 CE. 1.4 105 C


16. A parallel-plate capacitor has a plate area of 0.2m2 and a plate separation of 0.1mm. If thecharge on each plate has a magnitude of 4 106 C the potential dierence across the platesis approximately:

A. 0B. 4 102VC. 1 102VD. 2 102VE. 4 108V

17. The capacitance of a spherical capacitor with inner radius a and outer radius b is proportionalto:

A. a/bB. b aC. b2 a2D. ab/(b a)E. ab/(b2 a2)

18. The capacitance of a single isolated spherical conductor with radius R is proportional to:

A. RB. R2

C. 1/RD. 1/R2

E. none of these

19. Two conducting spheres have radii of R1 and R2, with R1 greater than R2. If they are farapart the capacitance is proportional to:

A. R1R2/(R1 R2)B. R21 R22C. (R1 R2)/R1R2D. R21 +R

22

E. none of these

20. The capacitance of a cylindrical capacitor can be increased by:

A. decreasing both the radius of the inner cylinder and the lengthB. increasing both the radius of the inner cylinder and the lengthC. increasing the radius of the outer cylindrical shell and decreasing the lengthD. decreasing the radius of the inner cylinder and increasing the radius of the outer cylindrical

shellE. only by decreasing the length


21. A battery is used to charge a series combination of two identical capacitors. If the potentialdierence across the battery terminals is V and total charge Q flows through the battery duringthe charging process then the charge on the positive plate of each capacitor and the potentialdierence across each capacitor are:A. Q/2 and V/2, respectivelyB. Q and V , respectivelyC. Q/2 and V , respectivelyD. Q and V/2, respectivelyE. Q and 2V , respectively

22. A battery is used to charge a parallel combination of two identical capacitors. If the potentialdierence across the battery terminals is V and total charge Q flows through the battery duringthe charging process then the charge on the positive plate of each capacitor and the potentialdierence across each capacitor are:A. Q/2 and V/2, respectivelyB. Q and V , respectivelyC. Q/2 and V , respectivelyD. Q and V/2, respectivelyE. Q and 2V , respectively

23. A 2-F and a 1-F capacitor are connected in series and a potential dierence is applied acrossthe combination. The 2-F capacitor has:

A. twice the charge of the 1-F capacitorB. half the charge of the 1-F capacitorC. twice the potential dierence of the 1-F capacitorD. half the potential dierence of the 1-F capacitorE. none of the above

24. A 2-F and a 1-F capacitor are connected in parallel and a potential dierence is appliedacross the combination. The 2-F capacitor has:

A. twice the charge of the 1-F capacitorB. half the charge of the 1-F capacitorC. twice the potential dierence of the 1-F capacitorD. half the potential dierence of the 1-F capacitorE. none of the above

25. Let Q denote charge, V denote potential dierence, and U denote stored energy. Of thesequantities, capacitors in series must have the same:

A. Q onlyB. V onlyC. U onlyD. Q and U onlyE. V and U only


26. Let Q denote charge, V denote potential dierence, and U denote stored energy. Of thesequantities, capacitors in parallel must have the same:

A. Q onlyB. V onlyC. U onlyD. Q and U onlyE. V and U only

27. Capacitors C1 and C2 are connected in parallel. The equivalent capacitance is given by:

A. C1C2/(C1 + C2)B. (C1 + C2)/C1C2C. 1/(C1 + C2)D. C1/C2E. C1 + C2

28. Capacitors C1 and C2 are connected in series. The equivalent capacitance is given by:

A. C1C2/(C1 + C2)B. (C1 + C2)/C1C2C. 1/(C1 + C2)D. C1/C2E. C1 + C2

29. Capacitors C1 and C2 are connected in series and a potential dierence is applied to thecombination. If the capacitor that is equivalent to the combination has the same potentialdierence, then the charge on the equivalent capacitor is the same as:A. the charge on C1B. the sum of the charges on C1 and C2C. the dierence of the charges on C1 and C2D. the product of the charges on C1 and C2E. none of the above

30. Capacitors C1 and C2 are connected in parallel and a potential dierence is applied to thecombination. If the capacitor that is equivalent to the combination has the same potentialdierence, then the charge on the equivalent capacitor is the same as:A. the charge on C1B. the sum of the charges on C1 and C2C. the dierence of the charges on C1 and C2D. the product of the charges on C1 and C2E. none of the above


31. Two identical capacitors are connected in series and two, each identical to the first, are con-nected in parallel. The equivalent capacitance of the series connection is the equivalentcapacitance of parallel connection.

A. twiceB. four timesC. halfD. one-fourthE. the same as

32. Two identical capacitors, each with capacitance C, are connected in parallel and the combi-nation is connected in series to a third identical capacitor. The equivalent capacitance of thisarrangement is:

A. 2C/3B. CC. 3C/2D. 2CE. 3C

33. A 2-F and a 1-F capacitor are connected in series and charged from a battery. They storecharges P and Q, respectively. When disconnected and charged separately using the samebattery, they have charges R and S, respectively. Then:

A. R > S > Q = PB. P > Q > R = SC. R > P = Q > SD. R = P > S = QE. R > P > S = Q

34. Capacitor C1 is connected alone to a battery and charged until the magnitude of the chargeon each plate is 4.0 108 C. Then it is removed from the battery and connected to two othercapacitors C2 and C3, as shown. The charge on the positive plate of C1 is then 1.0 108 C.The charges on the positive plates of C2 and C3 are:

C1C2

C3

A. q2 = 3.0 108 C and q3 = 3.0 108 CB. q2 = 2.0 108 C and q3 = 2.0 108 CC. q2 = 5.0 108 C and q3 = 1.0 108 CD. q2 = 3.0 108 C and q3 = 1.0 108 CE. q2 = 1.0 108 C and q3 = 3.0 108 C


35. Each of the four capacitors shown is 500F. The voltmeter reads 1000V. The magnitude ofthe charge, in coulombs, on each capacitor plate is:

......................................................................................................................................... V

A. 0.2B. 0.5C. 20D. 50E. none of these

36. The diagram shows four 6-F capacitors. The capacitance between points a and b is:

sa

s b

A. 3FB. 4FC. 6FD. 9FE. 1F

37. Each of the two 25-F capacitors shown is initially uncharged. How many coulombs of chargepass through the ammeter A after the switch S is closed?

4000V

.........................................................

S

.......................................................................................................................................

..................................................... A

A. 0.10B. 0.20C. 10D. 0.05E. none of these


38. A 20-F capacitor is charged to 200V. Its stored energy is:

A. 4000 JB. 4 JC. 0.4 JD. 2000 JE. 0.1 J

39. A charged capacitor stores 10C at 40V. Its stored energy is:

A. 400 JB. 4 JC. 0.2 JD. 2.5 JE. 200 J

40. A 2-F and a 1-F capacitor are connected in series and charged by a battery. They storeenergies P and Q, respectively. When disconnected and charged separately using the samebattery, they store energies R and S, respectively. Then:

A. R > P > S > QB. P > Q > R > SC. R > P > Q > SD. P > R > S > QE. R > S > Q > P

41. The quantity (1/2)60E2 has the significance of:A. energy/faradB. energy/coulombC. energyD. energy/volumeE. energy/volt

42. Capacitors A and B are identical. Capacitor A is charged so it stores 4 J of energy and capacitorB is uncharged. The capacitors are then connected in parallel. The total stored energy in thecapacitors is now:

A. 16 JB. 8 JC. 4 JD. 2 JE. 1 J


43. To store a total of 0.040 J of energy in the two identical capacitors shown, each should have acapacitance of:

200V

A. 0.10FB. 0.50F0.10FC. 1.0JD. 1.5FE. 2.0F

44. A battery is used to charge a parallel-plate capacitor, after which it is disconnected. Then theplates are pulled apart to twice their original separation. This process will double the:

A. capacitanceB. surface charge density on each plateC. stored energyD. electric field between the two placesE. charge on each plate

45. A parallel-plate capacitor has a plate area of 0.3m2 and a plate separation of 0.1mm. If thecharge on each plate has a magnitude of 5 106 C then the force exerted by one plate on theother has a magnitude of about:

A. 0B. 5NC. 9ND. 1 104NE. 9 105N

46. A certain capacitor has a capacitance of 5.0F. After it is charged to 5.0C and isolated, theplates are brought closer together so its capacitance becomes 10F. The work done by theagent is about:

A. zeroB. 1.25 106 JC. 1.25 106 JD. 8.3 107 JE. 8.3 107 J


47. A dielectric slab is slowly inserted between the plates of a parallel plate capacitor, while thepotential dierence between the plates is held constant by a battery. As it is being inserted:A. the capacitance, the potential dierence between the plates, and the charge on the positive

plate all increaseB. the capacitance, the potential dierence between the plates, and the charge on the positive

plate all decreaseC. the potential dierence between the plates increases, the charge on the positive plate de-

creases, and the capacitance remains the sameD. the capacitance and the charge on the positive plate decrease but the potential dierence

between the plates remains the sameE. the capacitance and the charge on the positive plate increase but the potential dierence

between the plates remains the same

48. An air-filled parallel-plate capacitor has a capacitance of 1 pF. The plate separation is thendoubled and a wax dielectric is inserted, completely filling the space between the plates. As aresult, the capacitance becomes 2 pF. The dielectric constant of the wax is:

A. 0.25B. 0.5C. 2.0D. 4.0E. 8.0

49. One of materials listed below is to be placed between two identical metal sheets, with no, airgap, to form a parallel-plate capacitor. Which produces the greatest capacitance?

A. material of thickness 0.1mm and dielectric constant 2B. material of thickness 0.2mm and dielectric constant 3C. material of thickness 0.3mm and dielectric constant 2D. material of thickness 0.4mm and dielectric constant 8E. material of thickness 0.5mm and dielectric constant 11

50. Two capacitors are identical except that one is filled with air and the other with oil. Bothcapacitors carry the same charge. The ratio of the electric fields Eair/Eoil is:

A. between 0 and 1B. 0C. 1D. between 1 and infinityE. infinite


51. A parallel-plate capacitor, with air dielectric, is charged by a battery, after which the batteryis disconnected. A slab of glass dielectric is then slowly inserted between the plates. As it isbeing inserted:

A. a force repels the glass out of the capacitorB. a force attracts the glass into the capacitorC. no force acts on the glassD. a net charge appears on the glassE. the glass makes the plates repel each other

ans: B

52. Two parallel-plate capacitors with the same plate separation but dierent capacitance areconnected in parallel to a battery. Both capacitors are filled with air. The quantity that isNOT the same for both capacitors when they are fully charged is:

A. potential dierenceB. energy densityC. electric field between the platesD. charge on the positive plateE. dielectric constant

ans: D

53. Two parallel-plate capacitors with the same plate area but dierent capacitance are connectedin parallel to a battery. Both capacitors are filled with air. The quantity that is the same forboth capacitors when they are fully charged is:

A. potential dierenceB. energy densityC. electric field between the platesD. charge on the positive plateE. plate separation

ans: A

54. Two parallel-plate capacitors with dierent plate separation but the same capacitance areconnected in series to a battery. Both capacitors are filled with air. The quantity that is NOTthe same for both capacitors when they are fully charged is:

A. potential dierenceB. stored energyC. electric field between the platesD. charge on the positive plateE. dielectric constant

ans: C

55. Two parallel-plate capacitors with dierent capacitance but the same plate separation areconnected in series to a battery. Both capacitors are filled with air. The quantity that is thesame for both capacitors when they are fully charged is:

A. potential dierenceB. stored energyC. energy densityD. electric field between the platesE. charge on the positive plate

ans: E


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