Physics Questions

88) If a charge of 11.4 C passes through a computer in 1.75 min, what is the average current through the computer?

0.109A

87) A 10-A current flows through a wire for 2.0 min. (e = 1.60 × 10-19 C) (a) How much charge has passed through this wire? (b) How many electrons have passed any point in the wire?

1. 1200C b. 7.5*10^21

34) An electric dipole consists of charges of ±6.00 µC that are 10.0 cm apart, as shown in the figure. Find the magnitude and direction of the electric field this dipole produces at point P, which is 7.00 cm from each charge. (k = 1/4πε0 = 8.99 × 109 N ∙ m2/C2)

1.57*10^7 N/C, to the left parallel to the line connecting the charges

93) When a thin copper wire that is 178 m long is connected between a 1.2-V potential difference, a current of 2.0 amps flows through the wire. What is the diameter of this wire? The resistivity of copper is 1.72 × 10-8 Ω ∙ m.

2.5 mm

26) An electron is placed in a uniform electric field of 4.5 × 104 N/C that points to the right. (e = 1.6 × 10-19 C, melectron = 9.11 × 10-31 kg) (a) What are the magnitude and direction of the force on the electron?

7.2*10^15 N to the left

31) The electric field at a point 2.8 cm from a small object points toward the object with a strength of 180,000 N/C. What is the object's charge q? (k = 1/4πε0 = 8.99 × 109 N ∙ m2/C2) A) -16 nC B) +16 nC C) -17 nC D) +17 nC

A) -16 nC

56) The three point charges shown in the figure form an equilateral triangle with sides 4.9 cm long. What is the electric potential (relative to infinity) at the point indicated with the dot, which is equidistant from all three charges? Assume that the numbers in the figure are all accurate to two significant figures. (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2) A) 0.00 V B) 1300 V C) 640 V D) 1900 V

A) 0.00 V

68) An ideal air-filled parallel-plate capacitor consists of two circular plates, each of radius How far apart should the plates be for the capacitance to be 300.0-pF? (ε0 = 8.85 × 10-12 C2/N ∙ m2) A) 0.0083 μm B) 0.0042 μm C) 0.00094 μm D) 0.00047 μm

A) 0.0083 μm

16) A piece of plastic has a net charge of +2.00 μC. How many more protons than electrons does this piece of plastic have? (e = 1.60 × 10-19 C) A) 1.25 × 1013 B) 1.25 × 1019 C) 2.50 × 1013 D) 2.50 × 1019 E) 3.01 × 1023

A) 1.25 × 1013

54) Two 3.0 μC charges lie on the x-axis, one at the origin and the other at What is the potential due to these charges at a point at on the x-axis? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2) A) 11,000 V B) 9000 V C) 14,000 V D) 3400 V

A) 11,000 V

21) Two equally charged tiny spheres of mass 1.0 g are placed 2.0 cm apart. When released, they begin to accelerate away from each other at What is the magnitude of the charge on each sphere, assuming only that the electric force is present? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2) A) 140 nC B) 120 nC C) 95 nC D) 75 nC

A) 140 nC

53) A sphere with radius 2.0 mm carries a charge. What is the potential difference, between point B, which is from the center of the sphere, and point A, which is from the center of the sphere? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2) A) 1500 V B) -1500 V C) 170 V D) -0.63 V

A) 1500 V

29) What is the magnitude of the electric field 2.8 cm from a tiny object that carries a charge of -16 nC? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2) A) 180,000 N/C B) 5100 N/C C) 1.8 × 1014 N/C D) -180,000 N/C E) -5100 N/C

A) 180,000 N/C

23) A small object with a 5.0-μC charge is accelerating horizontally on a friction-free surface at 0.0050 m/s2 due only to an electric field. If the object has a mass of 2.0 g, what is the magnitude of the electric field? A) 2.0 N/C B) 4.0 N/C C) 0.0020 N/C D) 0.0040 N/C E) 1.0 N/C

A) 2.0 N/C

49) If an electron is accelerated from rest through a potential difference of 1500 V, what speed does it reach? (e = 1.60 × 10-19 C , melectron = 9.11 × 10-31 kg) A) 2.3 × 107 m/s B) 1.9 × 107 m/s C) 1.5 × 107 m/s D) 1.1 × 107 m/s

A) 2.3 × 107 m/s

30) Two tiny particles having charges +20.0 μC and -8.00 μC are separated by a distance of 20.0 cm. What are the magnitude and direction of electric field midway between these two charges? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2) A) 25.2 × N/C directed towards the negative charge B) 25.2 × N/C directed towards the positive charge C) 25.2 × N/C directed towards the negative charge D) 25.2 × N/C directed towards the positive charge E) 25.2 × N/C directed towards the negative charge

A) 25.2 × N/C directed towards the negative charge

25) What is the magnitude of a the vertical electric field that will balance the weight of a plastic sphere of mass that has been charged to -3.0 nC? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2) A) 6.9 × 106 N/C B) 7.8 × 105 N/C C) 1.5 × 106 N/C D) 2.1 × 106 N/C

A) 6.9 × 106 N/C

69) Measurements show that it takes 0.30 mJ of work to move 5.0-μC of charge from one plate to another of a certain air-filled capacitor while the potential difference between these plates is kept constant. What is the potential difference between the plates of this capacitor? A) 60 V B) 81 V C) 55 V D) 23 V E) 0 V

A) 60 V

73) The square plates of a 3000-pF parallel-plate capacitor measure 40 mm by 40 mm and are separated by a dielectric that is 0.29 mm thick and completely fills the region between the plates. What is the dielectric constant of the dielectric? (ε0 = 8.85 × 10-12 C2/N ∙ m2) A) 61 B) 56 C) 50 D) 45 E) 67

A) 61

50) A proton with a speed of 2.0 x m/s accelerates through a potential difference and thereby increases its speed to 4.0 x m/s. Through what magnitude potential difference did the proton accelerate? (e = 1.60 × 10-19 C , mproton = 1.67 × 10-27 kg) A) 630 V B) 210 V C) 840 V D) 1000 V E) 100 V

A) 630 V

74) A capacitor has a voltage of applied across its plates, and then the voltage source is removed. What is the potential difference across its plates if the space between them is then filled with mica, having a dielectric constant of 5.4? A) 72 V B) 2110 V C) 641 V D) 18,675 V

A) 72 V

13) Three equal-magnitude point charges of varying signs are placed at the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the center of the square? A) A B) B C) C D) D

A) A

5) Four point charges of equal magnitudes but with varying signs are arranged on three of the corners and at the center of the square of side d as shown in the figure. Which one of the arrows shown represents the net force acting on the center charge? A) A B) B C) C D) D

A) A

84) Consider two copper wires of equal cross-sectional area. One wire has 3 times the length of the other. How do the resistivities of these two wires compare? A) Both wires have the same resistivity. B) The longer wire has 3 times the resistivity of the shorter wire. C) The longer wire has 9 times times the resistivity of the shorter wire. D) The longer wire has 27 times times the resistivity of the shorter wire.

A) Both wires have the same resistivity.

80) Copper wire #1 has a length L and a radius b. Copper wire #2 has a length 2L and a radius 2b. Which statement about the resistance across the ends of the wires is true? A) The resistance of wire #1 is twice as high as that of wire #2. B) The resistance of wire #1 is equal to that of wire #2. C) The resistance of wire #1 is half that of wire #2. D) The resistance of wire #1 is four times higher than that of wire #2.

A) The resistance of wire #1 is twice as high as that of wire #2.

11) The figure shows two unequal charges, +q and -Q. Charge -Q has greater magnitude than charge +q. Point X is midway between the charges. In what section of the line will there be a point where the resultant electric field is zero? A) VW B) WX C) XY D) YZ

A) VW

12) The electric field at point P due to a point charge Q a distance R away from P has magnitude E. In order to double the magnitude of the field at P, you could A) double the distance to 2R. B) double the charge to 2Q. C) reduce the distance to R/2. D) reduce the distance to R/4. E) double the charge to 2Q and at the same time reduce the distance to R/2.

A) double the distance to 2R.

39) Four charged particles (two having a charge +Q and two having a charge -Q) are arranged in the xy-plane, as shown in the figure. These particles are all equidistant from the origin. The electric potential (relative to infinity) at point P on the z-axis due to these particles, is A) zero. B) positive. C) negative. D) impossible to determine based on the information given.

A) zero.

8) Two small identically charged balls are a certain distance apart. The vectors in the figure show the magnitude and direction of the electrostatic force on each ball due to the other one. Suppose that the charge on the left ball is now doubled (represented by two plus signs). Which vector diagram below best represents the forces that now act on each of the two balls?

Ans: C... Two equal length lines points in opposite directions one with ++ and the other with +

7) Two equal and opposite charges are a small distance apart, forming an electric dipole. A positive charge +q is placed above these charges, as shown in the figure, equidistant from both of them. Which diagram below best gives the direction of the net force the dipole exerts on the charge +q?

Ans: arrow pointing to the right

92) The graph shown in the figure shows the results of measurements of the dc current through a circuit device for various potential differences across it. Assume that all the numbers shown are accurate to two significant figures. What is the resistance of this device?

Answer: 2.0 Ω

57) Four point charges of magnitude 6.00 μC and are at the corners of a square 2.00 m on each side. Two of the charges are positive, and two are negative. What is the electric potential at the center of this square, relative to infinity, due to these charges? (k = 1/4πε0 = 8.99 × 109 N ∙ m2/C2) A) 76.4 kV B) 0 V C) 153 kV D) 61.0 kV E) 306 kV

B) 0 V

96) A 120-m long metal wire having a resistivity of 1.68 × 10-8 Ω ∙ m has a resistance of 6.0 Ω. What is the diameter of the wire? A) 0.065 mm B) 0.65 mm C) 0.65 cm D) 0.65 m

B) 0.65 mm

24) A pair of charged conducting plates produces a uniform field of 12,000 N/C, directed to the right, between the plates. The separation of the plates is 40 mm. An electron is projected from plate A, directly toward plate B, with an initial speed of v0 = 2.0 × 107 m/s. What is the speed of the electron as it strikes plate B? (e = 1.6 × 10-19 C, melectron = 9.11 × 10-31 kg) A) 1.2 × 107 m/s B) 1.5 × 107 m/s C) 1.8 × 107 m/s D) 2.1 × 107 m/s E) 2.4 × 107 m/s

B) 1.5 × 107 m/s

48) A tiny particle with charge + 5.0 μC is initially moving at 55 m/s. It is then accelerated through a potential difference of 500 V. How much kinetic energy does this particle gain during the period of acceleration? A) 1.0 × 104 J B) 2.5 × 10-3 J C) 100 J D) 2500 J

B) 2.5 × 10-3 J

63) Consider a uniform horizontal electric field of 50 N/C directed toward the east. If the electric potential at a given point in the field is 80 V, what is the potential at a point 1.0 m directly east of the point? A) 15 V B) 30 V C) 90 V D) 130 V

B) 30 V

71) An air-filled capacitor has a potential difference between the plates of 80 V. If the charge on each of the plates of the capacitor has magnitude 8.0 μC, what is the electrical energy stored by this capacitor? A) 640 µJ B) 320 µJ C) 50 nJ D) 60 nJ E) 30 pJ

B) 320 µJ

14) Three equal-magnitude point charges of varying signs are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the vacant corner of the square? A) A B) B C) C D) D

B) B

43) When a certain capacitor carries charges of ±10 µC on its plates, the potential difference cross the plates is 25 V. Which of the following statements about this capacitor are true? (There could be more than one correct choice.) A) If we double the charges on the plates to ±20 µC, the capacitance of the capacitor will also double. B) If we double the charges on the plates to ±20 µC, the potential difference across the plates will also double. C) If we double the charges on the plates to ±20 µC, the capacitance of the capacitor will not change. D) If we double the charges on the plates to ±20 µC, the potential difference across the plates will decrease by a factor of two.

B) If we double the charges on the plates to ±20 µC, the potential difference across the plates will also double. C) If we double the charges on the plates to ±20 µC, the capacitance of the capacitor will not change.

46) The plates of a parallel-plate capacitor are maintained with constant voltage by a battery as they are pulled apart. What happens to the strength of the electric field between the plates during this process? A) It increases. B) It decreases. C) It remains constant. D) It cannot be determined from the information given.

B) It decreases.

78) The figure shows conventional current passing through a resistor. The arrow shows the direction in which this conventional current is flowing. Which of the following statements are correct? (There could be more than one correct choice.) A) The charges are moving slower at point b than at point a. B) The electric potential is lower at point b than at point a. C) The electric potential is higher at point b than at point a. D) The current at point b is the same as the current at point a. E) The electric potential at point b is the same as it is at point a.

B) The electric potential is lower at point b than at point a. D) The current at point b is the same as the current at point a.

97) A metal bar is 20 cm long and has a rectangular cross-section measuring 1.0 cm × 2.0 cm. What is the voltage drop along its length when it carries a 4000-A current? The resistivity of the metal is 1.68 × 10-8 Ω ∙ m. A) 0.67 V B) 0.34 V C) 0.067 V D) 0.034 V

C) 0.067 V

90) A total of 2.0 × 1013 electrons pass a given point in a wire in 15 s. What is the current in the wire? (e = 1.60 × 10-19 C) A) 1.3 mA B) 1.3 A C) 0.21 μA D) 3.2 μA

C) 0.21 μA

3) Two identical small charged spheres are a certain distance apart, and each one initially experiences an electrostatic force of magnitude F due to the other. With time, charge gradually diminishes on both spheres by leaking off. When each of the spheres has lost half its initial charge, what will be the magnitude of the electrostatic force on each one? A) 1/16 F B) 1/8 F C) 1/4 F D) 1/2 F E) 1/ F

C) 1/4 F

67) The potential difference between the plates of an ideal air-filled parallel-plate capacitor with a plate separation of 6.0 cm is 60 V. What is the strength of the electric field between the plates of this capacitor? A) 60 V/m B) 500 V/m C) 1000 V/m D) 2000 V/m E) 3600 V/m

C) 1000 V/m

75) A 6.0-μF air-filled capacitor is connected across a 100-V potential source (a battery). After the battery fully charges the capacitor, it is left connected and the capacitor is immersed in transformer oil, which has a dielectric constant of 4.5. How much additional charge flows from the battery onto the capacitor during this process? A) 1.2 mC B) 1.7 mC C) 2.1 mC D) 2.5 mC

C) 2.1 mC

17) The force of attraction that a -40.0 μC point charge exerts on a +108 μC point charge has magnitude 4.00 N. How far apart are these two charges? (k = 1/4πε0 = 8.99 × 109 N ∙ m2/C2) A) 2.10 m B) 3.67 m C) 3.12 m D) 2.49 m E) 1.13 m

C) 3.12 m

40) The electric potential at a distance of 4 m from a certain point charge is 200 V relative to infinity. What is the potential (relative to infinity) at a distance of 2 m from the same charge? A) 200 V B) 50 V C) 400 V D) 100 V E) 600 V

C) 400 V

59) In a region where the electric field is uniform and points in the +x direction, the electric potential is -2000 V at x = 8 m and is +400 V at x = 2 m. What is the magnitude of the electric field? A) 200 V/m B) 300 V/m C) 400 V/m D) 500 V/m E) 600 V/m

C) 400 V/m

89) How much charge must pass by a point in a wire in 10 s for the current in the wire to be 0.50 A? A) 20 C B) 2.0 C C) 5.0 C D) 0.050 C

C) 5.0 C

52) If it takes 50 J of energy to move 10 C of charge from point A to point B, what is the magnitude of the potential difference between points A and B? A) 500 V B) 50 V C) 5.0 V D) 0.50 V

C) 5.0 V

60) A battery maintains the electrical potential difference of 6.0-V between two large parallel metal plates separated by 1.0 mm. What is the strength of the electric field between the plates? A) 6.0 V/m B) 600 V/m C) 6000 V/m D) zero

C) 6000 V/m

58) Point charges +4.00 μC and +2.00 μC are placed at the opposite corners of a rectangle as shown in the figure. What is the potential at point A, relative to infinity, due to these charges? (k = 1/4πε0 = 8.99 × 109 N ∙ m2/C2) A) 0.899 kV B) 8.99 kV C) 89.9 kV D) 899 kV E) 8990 kV

C) 89.9 kV

70) An air-filled 20-μF capacitor has a charge of 60 μC on its plates. How much energy is stored in this capacitor? A) 70 μJ B) 80 μJ C) 90 μJ D) 100 μJ E) 110 μJ

C) 90 μJ

2) Two tiny beads are 25 cm apart with no other charges or fields present. Bead A carries 10 µC of charge and bead B carries 1 µC. Which one of the following statements is true about the magnitudes of the electric forces on these beads? A) The force on A is 10 times the force on B. B) The force on B is 10 times the force on A. C) The force on A is exactly equal to the force on B. D) The force on A is 100 times the force on B. E) The force on B is 100 times the force on A.

C) The force on A is exactly equal to the force on B.

45) An ideal parallel-plate capacitor consists of two parallel plates of area A separated by a distance d. This capacitor is connected across a battery that maintains a constant potential difference between the plates. If the separation between the plates is now doubled, the magnitude of the charge on the plates will A) double. B) quadruple. C) be cut in half. D) be cut in fourth. E) not change.

C) be cut in half.

47) Doubling the capacitance of a capacitor that is holding a constant charge causes the energy stored in that capacitor to A) quadruple. B) double. C) decrease to one-half. D) decrease to one-fourth.

C) decrease to one-half.

41) If the electric field between the plates of a given air-filled capacitor is weakened by removing charge from the plates, the capacitance of that capacitor A) increases. B) decreases. C) does not change. D) It cannot be determined from the information given.

C) does not change.

85) When the current through a resistor is increased by a factor of 4, the power dissipated by the resistor A) decreases by a factor of 4. B) decreases by a factor of 16. C) increases by a factor of 16. D) increases by a factor of 4. E) increases by a factor of 2.

C) increases by a factor of 16.

37) As an electron moves in the direction the electric field lines A) it is moving from low potential to high potential and gaining electric potential energy. B) it is moving from low potential to high potential and losing electric potential energy. C) it is moving from high potential to low potential and gaining electric potential energy. D) it is moving from high potential to low potential and losing electric potential energy. E) both its electric potential and electric potential energy remain constant.

C) it is moving from high potential to low potential and gaining electric potential energy.

10) Four tiny charged particles (two having a charge +Q and two having a charge -Q) are distributed on the x- and y-axes as shown in the figure. Each charge is equidistant from the origin. In which direction is the net electric field at the point P on the y-axis? A) directly up (in the +y direction) B) directly left (-x direction) C) upwards and towards the left D) upwards and towards the right E) The net field is zero, so there is no direction.

C) upwards and towards the left

22) The three point charges +4.0 μC, -5.0 μC, and -9.0 μC are placed on the x-axis at the points x = 0 cm, x = 40 cm, and x = 120 cm, respectively. What is the electrostatic force on the -9.0 μC charge due to the other two charges? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2) A) -0.55 N B) 0.55 N C) 0.64 N D) 0.41 N E) -0.41 N

D) 0.41 N

83) Which one of the following quantities is equivalent to 1 Ω? A) 1 J/s B) 1 W/A C) 1 V ∙ A D) 1 V/A E) 1 A ∙ s

D) 1 V/A

55) Two very small +3.00-μC charges are at the ends of a meter stick. Find the electric potential (relative to infinity) at the center of the meter stick. (k = 1/4πε0 = 8.99 × 109 N ∙ m2/C2) A) 0.00 V B) 2.70 × 104 V C) 5.40 × 104 V D) 1.08 × 105 V

D) 1.08 × 105 V

27) A particle with a charge of +4.0 μC has a mass of 5.0 g. What magnitude electric field directed upward will exactly balance the weight of the particle? A) 4.1 × 104 N/C B) 8.2 × 104 N/C C) 4.4 × 104 N/C D) 1.2 × 104 N/C E) 5.1 × 104 N/C

D) 1.2 × 104 N/C

33) A +5.0-μC point charge is placed at the 0 cm mark of a meter stick and a -4.0-μC charge is placed at the 50 cm mark. What is the net electric field at the 30 cm mark? (k = 1/4πε0 = 8.99 × 109 N ∙ m2/C2) A) 4.0 × 105 N/C B) 5.0 × 105 N/C C) 9.0 × 105 N/C D) 1.4 × 106 N/C

D) 1.4 × 106 N/C

100) How much does it cost to operate a 25-W soldering iron for 8.0 hours if energy costs 8.0¢/kWh? A) $1.50 B) 25¢ C) 16¢ D) 1.6¢

D) 1.6¢

62) Consider a uniform horizontal electric field of 50 N/C directed toward the east. If the electric potential measured at a given point is 80 V, what is the potential at a point 1.0 m directly west of that point? A) 30 V B) 50 V C) 80 V D) 130 V

D) 130 V

51) How much work is needed to carry an electron from the positive terminal to the negative terminal of a 9.0-V battery. (e = 1.60 × 10-19 C , melectron = 9.11 × 10-31 kg) A) 1.6 × 10-19 J B) 17 × 10-19 J C) 9.0 J D) 14.4 × 10-19 J E) 14.4 × 10-19 J/C

D) 14.4 × 10-19 J

72) If you want to store 2.0 mJ of energy in a 10-μF capacitor, how much potential do you need to put across it? A) 5.0 V B) 10 V C) 15 V D) 20 V

D) 20 V

66) What charge accumulates on the plates of a 2.0-μF air-filled capacitor when it is charged until the potential difference across its plates is 100 V? A) 50 μC B) 100 μC C) 150 μC D) 200 μC

D) 200 μC

86) A kilowatt-hour is equivalent to A) 1000 W. B) 3600 J. C) 3,600,000 J/s. D) 3,600,000 J. E) 3600 J/s

D) 3,600,000 J.

61) A uniform electric field, with a magnitude of 500 V/m, is points in the +x direction. If the potential at x = 5.0 m is 2500 V, what is the potential at x = 2.0 m? A) 0.50 kV B) 1.0 kV C) 2.0 kV D) 4.0 kV E) 5.0 kV

D) 4.0 kV

91) A 12-V battery is connected across a 100-Ω resistor. How many electrons flow through the wire in 1.0 min? (e = 1.60 × 10-19 C) A) 1.5 × 1019 B) 2.5 × 1019 C) 3.5 × 1019 D) 4.5 × 1019

D) 4.5 × 1019

42) An ideal parallel-plate capacitor has a capacitance of C. If the area of the plates is doubled and the distance between the plates is halved, what is the new capacitance? A) C/4 B) C/2 C) 2C D) 4C

D) 4C

64) Consider a uniform horizontal electric field of 50 N/C directed toward the east. If the electric potential at a given point in the field is 80 V, what is the potential at a point 1.0 m directly south of that point? A) 0 V B) 30 V C) 50 V D) 80 V

D) 80 V

6) Four point charges Q of equal magnitude and sign are arranged on three of the corners of the square of side d as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the upper right hand corner of the square? A) A B) B C) C D) D

D) D

44) Which of the following will increase the capacitance of a parallel-plate capacitor? (There could be more than one correct choice.) A) a decrease in the plate area and an increase in the plate separation B) a decrease in the potential difference between the plates C) an increase in the potential difference between the plates D) an increase in the plate area and a decrease in the plate separation E) an increase in the charge on the plates

D) an increase in the plate area and a decrease in the plate separation

82) A wire of resistivity ρ must be replaced in a circuit by a wire of the same material but four times as long. If, however, the total resistance is to remain as before, the diameter of the new wire must A) be the same as the original diameter. B) be one-half the original diameter. C) be one-fourth the original diameter. D) be two times the original diameter. E) be four times the original diameter.

D) be two times the original diameter.

36) As a proton moves in the direction the electric field lines A) it is moving from low potential to high potential and gaining electric potential energy. B) it is moving from low potential to high potential and losing electric potential energy. C) it is moving from high potential to low potential and gaining electric potential energy. D) it is moving from high potential to low potential and losing electric potential energy. E) both its electric potential and electric potential energy remain constant.

D) it is moving from high potential to low potential and losing electric potential energy.

15) Two stationary point charges q1 and q2 are shown in the figure along with a sketch of some field lines representing the electric field produced by them. What can you deduce from the sketch? A) q1 is negative and q2 is positive; the magnitudes are equal. B) q1 and q2 have the same sign; the magnitudes are equal. C) q1 is positive and q2 is negative; the magnitude of q1 is greater than the magnitude of q2. D) q1 is negative and q2 is positive; the magnitude of q1 is less than the magnitude of q2. E) q1 and q2 have the same sign; the magnitude of q1 is greater than the magnitude of q2.

D) q1 is negative and q2 is positive; the magnitude of q1 is less than the magnitude of q2.

1) If two objects are electrically attracted to each other, A) both objects must be negatively charged. B) both objects must be positively charged. C) one object must be negatively charged and the other object must be positively charged. D) the objects could be electrically neutral. E) None of the above statements are absolutely true.

D) the objects could be electrically neutral.

81) The figure shows a graph of the resistance of a wire as a function of its length. What physical quantities does the slope of this graph represent? A) the cross-sectional area of the wire B) the resistivity of the material of which the wire is made C) the product of the resistivity and the cross-sectional area of the wire D) the resistivity of the material divided by the cross-sectional area of the wire E) the reciprocal of the resistivity of the material

D) the resistivity of the material divided by the cross-sectional area of the wire

9) An electron is initially moving to the right when it enters a uniform electric field directed upwards, as shown in the figure. Which trajectory (X, Y, Z, or W) will the electron follow in the field? A) trajectory W B) trajectory X C) trajectory Y D) trajectory Z

D) trajectory Z

38) A proton is accelerated from rest through a potential difference V0 and gains a speed v0. If it were accelerated instead through a potential difference of 2V0, what speed would it gain? A) 8v0 B) 4v0 C) 2v0 D) v0*sqrt2

D) v0*sqrt2

28) A small styrofoam ball of mass 0.120 g is placed in an electric field of 6000 N/C pointing downward. What excess charge must be placed on the ball for it to remain suspended in the field? A) -16.0 nC B) -18.0 nC C) -57.2 nC D) -125 nC E) -196 nC

E) -196 nC

79) For the graph shown in the figure, what physical quantity does the slope of the graph represent for ohmic material? A) power B) resistivity C) 1/(resistivity) D) resistance E) 1/(resistance)

E) 1/(resistance)

20) Two point charges each experience a 1-N electrostatic force when they are 2 cm apart. If they are moved to a new separation of 8 cm, what is the magnitude of the electric force on each of them? A) 2 N B) 1/2 N C) 1/4 N D) 1/8 N E) 1/16 N

E) 1/16 N

18) When 1.0-µC point charge is 15 m from a second point charge, the force each one experiences a force of 1.0 µN. What is the magnitude of the second charge? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2) A) 25 C B) 1.0 C C) 10 nC D) 0.025 C E) 25 nC

E) 25 nC

32) A +5.00-μC point charge is placed at the 0.0 cm mark of a meter stick and a -4.00-μC point charge is placed at the 50.0 cm mark. At what point on a line through the ends of the meter stick is the electric field equal to zero? A) 1.4 m from the 0 cm mark B) 2.5 m from the 0 cm mark C) 2.9 m from the 0 cm mark D) 3.3 m from the 0 cm mark E) 4.7 m from the 0 cm mark

E) 4.7 m from the 0 cm mark

95) A certain metal wire has a cross-sectional area of 1.0 cm2 and a resistivity of 1.7 × 10-8 Ω ∙ m. How long would it have to be to have a resistance of 1.0 Ω? A) 5.9 × 106 m B) 5.9 m C) 5.9 × 104 m D) 590 m E) 5.9 km

E) 5.9 km

65) When the magnitude of the charge on each plate of an air-filled capacitor is 4 μC, the potential difference between the plates is 80 V. What is the capacitance of this capacitor? A) 0.1 µF B) 50 µF C) 100 µF D) 20 µF E) 50 nF

E) 50 nF

19) Two 10¢ coins (dimes) carrying identical charges are lying 2.5 m apart on a table. If each of these coins experiences an electrostatic force of magnitude 2.0 N due to the other coin, how large is the charge on each coin? (k = 1/4πε0 = 9.0 × 109 N ∙ m2/C2) A) 2.6 μC B) 26 μC C) 6.7 μC D) 5.2 μC E) 52 μC

E) 52 μC

4) Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are doubled and their separation is also doubled, what happens to the electrical force that each charge exerts on the other one? A) It increases by a factor of 2. B) It increases by a factor of . C) It is reduced by a factor of . D) It increases by a factor of 4. E) It remains the same.

E) It remains the same.

77) When a current flows through an ionic liquid such as salty water, the moving charges are A) only protons. B) only electrons. C) only negative ions. D) only positive ions. E) both positive and negative ions.

E) both positive and negative ions.

76) If a quantity you calculated has units of A ∙ s, what is that quantity? A) potential B) resistivity C) resistance D) capacitance E) charge

E) charge

35) Two large closely-spaced parallel metal plates are uniformly and oppositely charged and the electric field between them is 7.6 × 106 N/C. (a) What is the charge per unit area on each plate? (b) If the plates are now moved two times farther apart, what is the electric field between the plates?

a. +/- 67microC/m^2 b. 7.6*10^6 N/C (unchanged)

99) A resistor operated at 120 V dc is rated at 1.40 kW. (a) What is the normal operating current through the resistor? (b) What is the resistance of the resistor?

a. 11.7A b. 10.3 Omega

98) The power rating of a 400-Ω resistor is 0.800 W. (a) What is the maximum safe voltage across this resistor? (b) What is the maximum current the resistor can safely draw?

a. 17.9V b. 44.7mA

94) A 25-m wire of diameter 0.30 mm draws 0.499 A when connected across a 3.0-V potential difference. (a) What is the resistance of the wire? (b) What is the resistivity of the material from which the wire is made?

a. 6.0 omega b. 1.7 *10^8