Mark Reeves - Physics 22, Fall 2011 1 PracticeExam 4 ptphy21bio/Exams/practiceExam2...Mark Reeves -...

Mark Reeves - Physics 22, Fall 2011 1PracticeExam

4 pt

A point charge of mass 0.0699 kg and charge q = +6.87 µCis suspended by a thread between the vertical parallel platesof a parallel-plate capacitor, as shown in the figure below.

d

q

q

If the angle of deflection is θ = 24.6, and the separationbetween the plates is d = 0.0229 m, what is the potentialdifference between the plates?(in V)

1.A© 3.34 × 102

B© 4.45 × 102

C© 5.92 × 102

D© 7.87 × 102

E© 1.05 × 103

1) • E

• 1.05E+03

[1025.5591216728

1067.41867765944]

Sig 0 - 15

• Unit: V

4 pt

Two identical conducting spheres carry charges of +6.04 µCand -1.44 µC respectively. They are initially a large distanceL apart. The spheres are brought together, touched together,and then returned to their original separation L. What is theratio of the magnitude of the force on either sphere after theyare touched to that before they were touched?

2.A© 2.89 × 10−1

B© 4.19 × 10−1

C© 6.08 × 10−1

D© 8.82 × 10−1

E© 1.28

2) • C

• 6.08E-01

[0.596049484915379

0.620378035320089]

Sig 0 - 15

4 pt

An electron beam is deflected upward through 3.22 mm whiletraveling in a vacuum between two deflection plates 12.0 mmapart (the figure below ). The potential difference betweenthe deflecting plates is 123 kV and the kinetic energy of eachelectron as it enters the space between the plates is 1.69 ×

10−15 J. What is the kinetic energy of each electron when itleaves the space between the plates?

+

_

Electron beam Deflection

(in J)

3.A© 4.84 × 10−15

B© 5.46 × 10−15

C© 6.17 × 10−15

D© 6.98 × 10−15

E© 7.88 × 10−15

3) • D

• 6.98E-15

[6.83785298e-15

7.11694902e-15]

Sig 0 - 15

• Unit: J

4 pt

Find the electric potential energy for the following array ofcharges:

charge q1 = +4.08 µC is located at (x, y) = (0.0, 0.0) m;charge q2 = +3.17 µC is located at (3.92, 3.07) m;and charge q3 = -1.05 µC is located at (0.0, 3.07) m.(in J)

4.A© 2.19 × 10−3

B© 3.17 × 10−3

C© 4.60 × 10−3

D© 6.67 × 10−3

E© 9.67 × 10−3

4) • B

• 3.17E-03

[0.00310964484740956

0.00323656912689566]

Sig 0 - 15

• Unit: J


Two uniformely charged spheres are suspended by strings oflength L from vertically adjustable supports. The spheresare in static equilibrium and at the same height, as shownbelow.

Q T

W Z

4 pt The angles with respect to the vertical are Q=11.1,

and T=21.3.

⊲ The amount of charge on Z can be equal to that on W.5. A© True B© False C© Cannot tell

⊲ The charge on W can be positive and that on Z negative.6. A© True B© False C© Cannot tell

⊲ The amount of charge on Z can be greater than that on W.7. A© True B© False C© Cannot tell

⊲ The charge on W can be positive and that on Z positive.8. A© True B© False C© Cannot tell

⊲ The mass of W can be less than that of Z.9. A© True B© False C© Cannot tell

4 pt The tension in the string supporting sphere W is 2.75E-

5 N. Calculate the tension in the other string.(in N)

10.A© 5.97 × 10−6

B© 7.46 × 10−6

C© 9.33 × 10−6

D© 1.17 × 10−5

E© 1.46 × 10−5

5) • A

• True

6) • B

• False

7) • A

• True

8) • A

• True

9) • B

• False

10) • E

• 1.46E-05

[1.42834120372213e-05

1.48664084469039e-05]

Sig 0 - 15

• Unit: N

4 pt Three arrangements of capacitors with capacities

indicated (in µF) are shown in the figure below.

43

2823

66

66

66

7.0 9.4 8.2

Rank their equivalent capacitances in order of INCREASINGvalue. (smallest has rank 1)

⊲ Capacitance of configuration X.11. A© Rank 1 B© Rank 2 C© Rank 3

⊲ Capacitance of configuration Y.12. A© Rank 1 B© Rank 2 C© Rank 3

⊲ Capacitance of configuration Z.13. A© Rank 1 B© Rank 2 C© Rank 3

11) • C

• 3

12) • A

• 1

13) • B

• 2


4 pt Which statements regarding a plate capacitor are true?

⊲ The charge of a disconnected charged plate capacitor in-creases when the plates are pulled apart

14. A© True B© False

⊲ The capacitance is proportional to the area15. A© True B© False

⊲ The capacitance is proportional to the gap width16. A© True B© False

⊲ The voltage across a disconnected charged plate capacitorincreases when the plates are pulled apart


⊲ The capacitance depends on the material between theplates.


14) • B

• False

15) • A

• True

16) • B

• False

17) • A

• True

18) • A

• True

A capacitor is completely charged with 680 nC by a voltagesource that had 225 V.

4 pt What is its capacitance? (in F)

19.A© 2.21 × 10−9

B© 2.58 × 10−9

C© 3.02 × 10−9

D© 3.54 × 10−9

E© 4.14 × 10−9

4 pt Now the plates of the charged capacitor are pushed to-

gether with the voltage source already disconnected.

20. A© The energy stored in the capacitor remains thesame.B© The capacitance increases.C© The charge on the plates increases.D© The voltage drop between the plates increases.E© None of the above.

4 pt The initial air gap of the capacitor above was 8 mm.

What is the stored energy if the air gap is now 2 mm? (in J)

21.A© 0.00 B© 1.91 × 10−5

C© 1.38 × 10−4

D© 3.06 × 10−4

E© 3.63 × 10−4

19) • C

• 3.02E-09

[2.87111111111111e-09

3.17333333333333e-09]

Sig 0 - 15

• Unit: F

20) • B

• false

• true

• false

• false

• false

21) • B

• 1.91E-05

[1.816875e-05

2.008125e-05]

Sig 0 - 15

• Unit: J

A 5-year old has nothing betterto do than to connect three capacitors to a voltage sourceas shown. The capacitors have C

1=58 mF, C

2=70 mF, and

C3=18 mF, respectively, and the voltage source has 4 Volts.

4 pt What is the total capacitance? (in mF)

22.A© 26.5 B© 31.0 C© 36.3 D© 42.5

E© 49.7


4 pt What is the total energy stored in the capacitors? (in

mJ)

23.A© 398 B© 465 C© 544 D© 637 E© 745

22) • E

• 49.7

[47.2328125

52.2046875]

Sig 0 - 15

• Unit: mF

23) • A

• 398

[377.8625

417.6375]

Sig 0 - 15

• Unit: mJ

+ -O

Q

P R

S

Two charges of equal magnitude are located on the horizontalaxis at equal distances from the vertical axis.

4 pt At what location does the electric field point due west?

24. A© PB© SC© OD© None of the locations

4 pt Where does the electric field point at location R?

25. A© WestB© SouthC© EastD© NorthE© No field

24) • A

• true

• false

• false

• false

25) • A

• true

• false

• false

• false

• false

The figure shows the equipotential lines of a charge distribu-tion and labelled locations.

ED C

AB

4 pt

Where do you expect the strongest electric field?

26. A© AB© BC© CD© DE© E

4 pt What is the direction of the electric field at A?

27. A© Approximately parallel to the x-axis.B© Approximately parallel to the y-axis.C© No field.


4 pt What is the direction of the electric field at E?

28. A© Approximately parallel to the x-axis.B© Approximately parallel to the y-axis.C© No field.

26) • E

• false

• false

• false

• false

• true

27) • B

• false

• true

• false

28) • A

• true

• false

• false

The following figure shows the electric field lines of two pointcharges:

D

A

C B

4 pt

Closest to which one of the locations would you expect noelectric field?

29. A© AB© BC© CD© DE© Nowhere.

4 pt

The electric field at location A is ...

30. A© ... stronger than at location CB© ... about the same strength as at location C, andneither is zero.C© ... weaker than at location C, but not zero.D© ... zero.

29) • D

• false

• false

• false

• true

• false

30) • A

• true

• false

• false

• false

A constant electric field of magnitude E = 306 V/m pointsin the positive x-direction. A charge Q is moved in positivex-direction within the field by an external force.

4 pt

31. A© The work required is inversely proportional to thedistance travelled.B© The work required is directly proportional to thedistance travelled.C© Without an external force, a free negative chargewould accelerate perpendicular to the depicted path.D© Without an external force, a free negative chargewould accelerate in the direction of the depicted path.E© The work required is proportional to the square ofthe charge.


4 pt How much work by an external force does it take to

move the charge Q = 11µC from x1= 0.07 m to x

2= 0.32 m?

(in J)

32.A© −1.76 × 10−3

B© −1.45 × 10−3

C© −8.42 × 10−4

D© −7.07 × 10−4

E© 4.29 × 10−4

31) • B

• false

• true

• false

• false

• false

32) • C

• -8.42E-04

[-0.000799425

-0.000883575]

Sig 0 - 15

• Unit: J

4 pt

a b c

d

e

Consider the arrangement of two fixed point charges, equalin magnitude, shown in the figure. Which of the followingstatements are correct for the initial motion of a third chargeif it is released from rest in the vicinity of the two chargesshown?

⊲ A negative charge at point e will accelerate up.33. A© True B© False

⊲ A negative charge at point d will accelerate down.34. A© True B© False

⊲ A positive charge at point c will accelerate toward the lower-left.


⊲ A positive charge at point a will accelerate toward the lower-left.


⊲ A negative charge at point b will accelerate down.37. A© True B© False

33) • A

• True

34) • B

• False

35) • B

• False

36) • B

• False

37) • A

• True


4 pt Three charges, Q1, Q2, and Q3 are located in a straight

line. The position of Q2 is 0.301 m to the right of Q1. Q3 islocated 0.169 m to the right of Q2. The force on Q2 due toits interaction with Q3 is directed to the.....

⊲ Left if the two charges are positive.38. A© True B© False

⊲ Left if the two charges are negative.39. A© True B© False

⊲ Left if the two charges have opposite signs.40. A© True B© False

⊲ Right if the two charges have opposite signs.41. A© True B© False

⊲ Right if the two charges are negative.42. A© True B© False

4 pt In the above problem, Q1= 1.90·10-6 C, Q2= -2.46·10-6

C, and Q3= 3.03·10-6 C. Calculate the total force on Q2. Givewith the plus sign for a force directed to the right.

(in N)

43.A© 1.30 B© 1.47 C© 1.67 D© 1.88

E© 2.13

4 pt Now the charges Q1= 1.90·10-6 C and Q

2= -2.46·10-6

C are fixed at their positions, distance 0.301 m apart, andthe charge Q

3= 3.03·10-6 C is moved along the straight line.

For what position of Q3

relative to Q1

is the net force on Q3

due to Q1

and Q2

zero? Use the plus sign for Q3

to the rightof Q

1.

(in m)

44.A© -1.51 B© -1.71 C© -1.93 D© -2.18

E© -2.47

38) • A

• True

39) • A

• True

40) • B

• False

41) • A

• True

42) • B

• False

43) • D

• 1.88

[1.8259385810573

1.93888323555569]

Sig 0 - 15

• Unit: N

44) • D

• -2.18

[-2.1177958288251

-2.24879350895862]

Sig 0 - 15

• Unit: m


4 pt c

a

b

Consider two uniformly charged parallel plates as shown inthe figure. The magnitudes of the charges are equal. SelectTrue or False for the following statements.

⊲ If the plates are oppositely charged, there is no electric fieldat c.


⊲ If both plates are positively charged, there is no electricfield at b.


⊲ If both plates are negatively charged, the electric field at a

points towards the top of the page47. A© True B© False

4 pt

If the plates are 1.0 cm by 1.0 cm squares, and the charges onthe plates are +/- 2.2 µC respectively, what is the magnitudeof the electric field at b? Assume that the spacing betweenthe plates is much less than 1 cm.(in V/m)

48.A© 1.057 × 109

B© 1.405 × 109

C© 1.869 × 109

D© 2.486 × 109

E© 3.306 × 109

45) • A

• True

46) • A

• True

47) • B

• False

48) • D

• 2.486E+09

[2436158192.0904

2535593220.33898]

Sig 0 - 15

• Unit: V/m

4 pt Consider a sphere of radius R = 7.16 m where a charge

of Q = 12.7 µC is uniformly distributed through the volumeof the sphere. What is the magnitude of the electric fieldat a point halfway between the center of the sphere and itssurface?(in V/m)

49.A© 1.11 × 103

B© 1.61 × 103

C© 2.34 × 103

D© 3.39 × 103

E© 4.92 × 103

49) • A

• 1.11E+03

[1091.27309540901

1135.81485440529]

Sig 0 - 15

• Unit: V/m

A solid metal sphere of radius a = 1.30 cm is surrounded bya concentric spherical metal shell of inner radius b = 1.80 cmand outer radius c = 2.30 cm. The inner sphere has a netcharge of Q

1= 4.10 µC, and the outer spherical shell has a

net charge of Q2

= -7.40 µC.

cb

a

4 pt What is the radial component of the electric field Er

at

a point located at radius r = 1.50 cm, i.e. between the twoconductors? E

ris positive if it points outward, negative if it

points inward.(in N/C)

50.A© 6.96 × 107

B© 9.26 × 107

C© 1.23 × 108

D© 1.64 × 108

E© 2.18 × 108

4 pt What is Er

at a point located at radius r = 2.70 cm,

i.e. outside the outer shell?(in N/C)

51.A© −1.67 × 107

B© −2.08 × 107

C© −2.60 × 107

D© −3.26 × 107

E© −4.07 × 107


4 pt What is the surface charge density, σb, on the inner

surface of the outer spherical conductor?(in C/m^2)

52.A© −6.18 × 10−4

B© −6.98 × 10−4

C© −7.89 × 10−4

D© −8.91 × 10−4

E© −1.01 × 10−3

4 pt What is the surface charge density, σc, on the outer

surface of the outer spherical conductor?(in C/m^2)

53.A© −3.04 × 10−4

B© −3.44 × 10−4

C© −3.89 × 10−4

D© −4.39 × 10−4

E© −4.96 × 10−4

50) • D

• 1.64E+08

[161360511.111111

166275044.444445]

Sig 0 - 15

• Unit: N/C

51) • E

• -4.07E+07

[-40085041.1522634

-41305905.3497942]

Sig 0 - 15

• Unit: N/C

52) • E

• -1.01E-03

[-0.000991893885303425

-0.00102210385135328]

Sig 0 - 15

• Unit: C/m^2

53) • E

• -4.96E-04

[-0.000488972724499249

-0.000503865294788567]

Sig 0 - 15

• Unit: C/m^2

4 pt

+q

-q

+q

-q+q

-q +q

-q

d

*

*

L

Figure 1

*

*

Figure 2

a

b

c

Consider two separate systems, each with four charges ofmagnitude q arranged in a square of length L as shown above.Points a and c are in the center of their squares while pointsb and d are half way between the lower two charges. Com-plete the following statements.

⊲ The electric potential at a is ....54. A© Positive B© Negative C© Zero

⊲ The electric potential at c is ....55. A© Positive B© Negative C© Zero

⊲ The electric potential at d is ....56. A© Positive B© Negative C© Zero

⊲ The electric potential at b is ....57. A© Positive B© Negative C© Zero

54) • C

• Zero

55) • C

• Zero

56) • A

• Positive

57) • C

• Zero


4 pt x (meters)

Vo

ltag

e (v

olt

s)

5 100

4

2

0

-2

What is the electric field at the point x=6.5 m? PositiveE-fields point to the right.(in V/m)

58.A© −4.43 × 10−1

B© −6.42 × 10−1

C© −9.31 × 10−1

D© -1.35 E© -1.96

58) • D

• -1.35

[-1.0125

-1.6875]

Sig 0 - 15

• Unit: V/m

4 pt The figure below shows identical light bulbs connected

to a battery. All the bulbs are glowing. Rank the brightnessof the bulbs, from brightest (rank 1) to dimmest (rank 5).

⊲ bulb E59. A© Rank 1 B© Rank 2 C© Rank 3

D© Rank 4 E© Rank 5

⊲ bulb D60. A© Rank 1 B© Rank 2 C© Rank 3


⊲ bulb A61. A© Rank 1 B© Rank 2 C© Rank 3


⊲ bulb B62. A© Rank 1 B© Rank 2 C© Rank 3


⊲ bulb F63. A© Rank 1 B© Rank 2 C© Rank 3


59) • E

• 5

60) • B

• 2

61) • A

• 1

62) • C

• 3

63) • D

• 4


4 pt In the circuit above,

the magnitudes of the currents through R1, R2, R3 areI1, I2, I3, respectively. Which one of the following equationsis always true?

64. A© I2 = I3 · R2/R3

B© I2 = I1 · R2/R3

C© I1 = I2 = I3

D© I1 ≥ I3

E© I2 = I3

64) • D

• false

• false

• false

• true

• false

4 pt In the circuit below, a constant current of i = 2.37 A

flows from b to c through the 8 Ω resistor.

8

7

25

Calculate the potential difference between points a and d.(in V)

65.A© 1.46 × 102

B© 1.94 × 102

C© 2.58 × 102

D© 3.43 × 102

E© 4.57 × 102

65) • A

• 1.46E+02

[143.0058

148.842771428572]

Sig 0 - 15

• Unit: V

4 pt Consider the circuit shown in the figure. Calculate the

potential difference across R4. Use the following data: R

1=

27.0 Ω, R2

= 18.5 Ω, R3

= 19.0 Ω, R4

= 25.5 Ω, ε = 25.0 V.

(in V)

66.A© 4.71 B© 5.88 C© 7.35

D© 9.19 E© 1.15 × 101

4 pt

Calculate the current in R2.

(in A)

67.A© 2.67 × 10−1

B© 3.56 × 10−1

C© 4.73 × 10−1

D© 6.29 × 10−1

E© 8.37 × 10−1

66) • E

• 1.15E+01

[11.2612162028325

11.7208576804991]

Sig 0 - 15

• Unit: V

67) • A

• 2.67E-01

[0.262058037040706

0.27275428345053]

Sig 0 - 15

• Unit: A


4 pt Two batteries (V1

= 15 V and V2

= 12 V) are in a

circuit with three identical resistors (R1

= R2

= R3

= 5.7 Ω).What is the current in the R

3resistor? Note that all resistor

values are equal, which greatly simplifies your loop equations.

(in A)

68.A© 2.281 B© 2.851 C© 3.564 D© 4.454

E© 5.568

68) • A

• 2.281

[2.16666666666666

2.39473684210526]

Sig 0 - 15

• Unit: A

4 pt Consider the circuit shown below, with a battery and

three identical light bulbs, and a switch connecting the thirdbulb to the circuit. Initially, the switch is open. Now,we are going to close the switch. Which of the follow-ing statements are true when the switch is closed (com-pared to the initial state, when the switch was open)?

⊲ Bulb #3, which was initially on, now goes out completely.69. A© True B© False

⊲ The total power dissipated in the circuit increases.70. A© True B© False

⊲ The voltage across bulb #2 does not change.71. A© True B© False

⊲ Bulb #2 gets dimmer than before, but does not go out.72. A© True B© False

⊲ The current through the battery decreases.73. A© True B© False

69) • B

• False

70) • A

• True

71) • A

• True

72) • B

• False

73) • B

• False

Printed from LON-CAPA©MSU Licensed under GNU General Public License

Mark Reeves - Physics 22, Fall 2011 1 PracticeExam 4 ptphy21bio/Exams/practiceExam2...Mark Reeves -...

Documents

Transcript of Mark Reeves - Physics 22, Fall 2011 1 PracticeExam 4 ptphy21bio/Exams/practiceExam2...Mark Reeves -...