PHYS222 Exam 1

In the circuit shown, two capacitors and a resistor in series are connected to a battery. Initially the switch is open. What is the current through the resistor a long time after the switch has been closed? 1 A 0 A 1.25*10-5 A 5*10-5 A 4 A

0 A

In the early universe and in stars, deuterium nuclei are produced from the combination of one proton and one neutron, with the release of a gamma ray. What is the charge on a deuterium nucleus in units of qe = 1.6*10-19 C? 0 -1 1 2 -2

1

The figure shows a uniform magnetic field directed into the plane of the paper. A particle with a positive charge moves in the plane. Which of the three paths does the particle follow? 1 2 3 none

1

Every minute, 120 C of charge flow through this cross section of the wire. The wire's current is 240A 120A 60A 2A

2A

In the circuit below, what is the current through R1? 10A zero 5A 2A 7A

2A

The diagram below shows a segment of a circuit. What is the current in the 200 Ohm resistor? 0.5A 1A 1.5A 2A none

2A

Determine the equivalent resistance of the circuit as shown 1 2 4 6

6

Three charges shown in Figure 18.4 form an equilateral triangle with 4.9 cm long sides. What is the electric potential at the point indicated with the dot? A) zero B) 1,300 V C) 640 V D) 1,900 V

A) zero

A compass is placed at the black dot. In which direction will the compass point?

B

The capacitors in the network shown in the figure all have a capacitance of 5.0 μF. What is the equivalent capacitance, Cab, of this capacitor network? A) 5.0 μF B) 20 μF C) 10 μF D) 1.0 μF E) 3.0 μF

E) 3.0 μF

What is the equivalent resistance in the circuit shown in the figure? A) 50 Ω B) 80 Ω C) 55 Ω D) 35 Ω

A) 50 Ω

A small glass bead has been charged to 1.9 nC. What is the strength of the electric field 2.0 cm from the center of the bead? A) 4.3 ×104 N/C B) 8.5 ×102 N/C C) 8.1 ×10-5 N/C D) 8.5 ×10-7 N/C

A) 4.3 ×104 N/C

Which of the diagrams represents resistors connected in series? (a) and (b) only (a) only (b) only (c) only all diagrams

(b) only

A bulb (i.e., a resistor) is connected in series to a switch, a battery, and an uncharged capacitor. At t = 0, the switch is closed. Which of the following best describes the brightness of the bulb as a function of time? (a) The current is constant since the battery voltage is constant. (c) (b) (d)

(c)

Each of three objects has a net charge. Objects A and B attract one another. Objects B and C also attract one another, but objects A and C repel one another. Which one of the following table entries is a possible combination of the signs of the charges on these three objects? A B C - - + + - - - + + - + - + + -

- + -

Which of the points shown in the figure below are at the same potential? 2 and 5. 2 and 4. 1 and 4. 2, 3, and 5. 1 and 5.

1 and 4.

What is the ratio of Vb/Va of the electric potentials at the two points? (A- 1mm, B-3mm) 9 3 1/3 1/9

1/3

A 120-V, 60-W incandescent light bulb; a 120-V, 120-W incandescent light bulb; and a 120-V, 240-W incandescent light bulb are connected in parallel as shown. The voltage between points a and b is 120 V. ?Which bulb glows the brightest 120-V, 60-W incandescent light bulb 120-V, 120-W incandescent light bulb 120-V, 240-W incandescent light bulb all three are equal

120-V, 240-W incandescent light bulb

The current through the 3 Ohm resistor is 9A 6A 5A 3A 1A

1A

The figure shows a uniform magnetic field directed into the plane of the paper. If the particle has a negative charge, which of the three paths does the particle follow? 1 2 3 none

3

What is the equivalent capacitance Ceq of the combination below 3/2C 2/3C 3C 1/3C 1/2C

3/2C

A 12-uF capacitor and a 6-uF capacitor are connected together as shown. What is the equivalent capacitance of the two capacitors as a unit? 18 9 6 4 2

4 uF

The figure below shows different ways to connect a light bulb to a battery with wires. Which of the bulbs will light up? 2 3 5 4 1

5

Where an electric field line crosses an equipotential surface, the angle between the field line and the equipotential is 180°. between zero and 90°. unknown. Not enough information given to decide. zero. 90°.

90°.

Which of the following statements is true? A positive charge experiences a repulsive force, away from a nearby conductor. A positive charge experiences an attractive electrostatic force toward a nearby neutral conductor. Whatever the force on a positive charge near a neutral conductor, the force on a negative charge is then oppositely directed. A positive charge experiences no electrostatic force near a neutral conductor.

A positive charge experiences an attractive electrostatic force toward a nearby neutral conductor.

Two electrons are passing 20 mm apart. What is the electric repulsive force that they exert on each other? (The value of k is 9 ×109 N.m2/C2) A) 5.8 ×10-25 N B) 2.3 ×1010 N C) 2.3 N D) 5.8 ×10-27 N

A) 5.8 ×10-25 N

Assume that the potential V is higher at point A than at point B. Which statement then is correct? A positive charge gains electrostatic potential energy when it moves from point B to point A. Any charge can move along an equipotential line from point A to point B and neither gain or lose electrostatic potential energy. An externall force has to do positive work to move a positive charge from point A to point B. A negative charge gains electrostatic potential energy when it moves from point B to point A.

A positive charge gains electrostatic potential energy when it moves from point B to point A.

The resistivity of gold is 2.44 ×10-8 Ohm-m at a temperature of 20°C. A gold wire, 0.5 mm in diameter and 44 cm long, carries a current of 380 ma. The number of electrons per second passing a given cross section of the wire, is closest to: A) 2.4 ×1018 B) 2.4 ×1017 C) 1.2 ×1022 D) 2.8 ×1014 E) 6.3 ×1015

A) 2.4 ×1018

Two capacitors, one a 4.0 μF capacitor, C1, and the other a 7.0 μF capacitor, C2, are connected in series. If a 90.0 V voltage source is applied to the capacitors, as shown in Figure 18.7, find the voltage drop across the 4.0 μF capacitor. A) 54 V B) 36 V C) 60 V D) 9.0 V

A) 54 V

Two point charges Q1 and Q2 of equal magnitudes and opposite signs are positioned as shown inthe figure. Which of the arrows best represents the net electric field at point P due to these twocharges?A) A B) B C) C D) D E) The field is equal to zero at point P.

A) A

Identical light bulbs are attached to identical batteries, as shown in Figure 19.7. The ranking (from lowest to highest) of the total power emitted from the light bulb(s) is A) B, A, C B) A, B, C C) C, B, A D) A, C, B E) C, A, B

A) B, A, C

Figure shows electric field lines arising from two small charged particles P and Q. Consider the following two statements: i. The charge on P is smaller than the charge on Q. ii. The electrostatic force on P is smaller than that on Q. Which of the above statements are true? A) Only i. B) Only ii. C) Both i and ii. D) Neither i nor ii.

A) Only i.

Suppose a region of space has a uniform electric field, directed towards the right, as shown in the figure. Which statement about the electric potential is true? A) The potential at points A and B are equal, and the potential at point C is lower than the potential at point A. B) The potential at point A is the highest, the potential at point B is the second highest, and the potential at point C is the lowest. C) The potential at all three locations (A, B, C) is the same because the field is uniform. D) The potential at points A and B are equal, and the potential at point C is higher than the potential at point A.

A) The potential at points A and B are equal, and the potential at point C is lower than the potential at point A.

Four charged particles (two having a charge +Q and two having a charge -Q) are distributed on the xy-plane, as shown in Figure 18.6. The charges are equidistant from the origin. The voltage is zero at infinity. The voltage at location P, which is on the zaxis, is A) zero. B) positive. C) negative. D) impossible to determine based on the information given.

A) zero.

A negatively charged rod is brought near a neutral metal sphere. Which of the following is true? A. There is an attractive force between the rod and sphere. B. There is a repulsive force between the rod and sphere. C. There is no electric force between the rod and sphere.

A. There is an attractive force between the rod and sphere.

Three point charges lie at the vertices of an equilateral triangle as shown. All three charges have the same magnitude, but charge #1 is positive (+q) and charges #2 and #3 are negative (-q). The net electric force that charges #2 and #3 exert on charge #1 is in A. the +x-direction. B. the -x-direction. C. the +y-direction. D. the -y-direction. E. none of the above.

A. the +x-direction.

Equipotential lines around two point charges are shown. What is the direction of the electric field at points A ans B? A: to the right B: to the right A: to the left B: down A: to the rightB: to the left The electric field has no direction. A: to the right B: up

A: to the right B: up

Which of the following statements about a conductor in electrostatic equilibrium is false? (a) The electric field inside the conductor is zero. (b) Just outside the conductor, the electrostatic field is perpendicular to its surface. (c) The net charge inside the conductor is zero, all excess charge resides on the surface. (d) A charge located within a hole in a conductor at equilibrium feels no force from charges outside the conductor.

All the above statements are true.

Three equal charges +Q are at three of the corners of a square of side d. A fourth charge +Q of equal magnitude is at the center of the square as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the center of the square? A) A B) B C) C D) D

B) B

X and Y are two initially uncharged metal spheres on insulating stands, and they are in contact witheach other. A positively charged rod R is brought close to X as shown in part (a) of the figure. SphereY is now moved away from X, as shown in part (b). What are the final charge states of X and Y? A) X is neutral and Y is positive. B) X is negative and Y is positive. C) Both X and Y are negative. D) X is positive and Y is neutral. E) Both X and Y are neutral.

B) X is negative and Y is positive.

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

B) resistance

Two small objects each with a net charge of Q exert a force of magnitude F on each other. We replace one of these with a charge 4Q. What is the magnitude of the force after the replacement? A. 16F B. 4F C. F D. F/4 E. None of the above

B. 4F

Two small objects each with a net charge of Q exert a force of magnitude F on each other. If the distance between these charges is reduced to one third, what will be the magnitude of the force? A. 27F B. 9F C. F D. F/9 E. None of the above

B. 9F

Earth and Moon attract each other via the gravitational force. Which force diagram correctly represents the magnitude and direction of the force on each of these objects?A. A B. B C. C D. D E. None of them

B. B

At a distance D from a very long uniform line of charge, the electric force is 1000 N. At what distance from the line will the force be 4000 N? A. 2D B. D/2 C. 4D D. D/4

B. D/2

The electric potential energy of two point charges approaches zero as the two point charges move farther away from each other. If the three point charges shown here lie at the vertices of an equilateral triangle, the electric potential energy of the system of three charges is A. positive. B. negative. C. zero. D. either positive or negative. E. either positive, negative, or zero.

B. negative.

A long, straight wire extends into and out of the screen. The current in the wire is A. into the screen B. out of the screen C. there is no current in the wire D not enough info

B. out of the screen

When a negative charge moves opposite to the direction of the electric field, A. the field does positive work on it and the potential energy increases. B. the field does positive work on it and the potential energy decreases. C. the field does negative work on it and the potential energy increases. D. the field does negative work on it and the potential energy decreases. E. the field does zero work on it and the potential energy remains constant.

B. the field does positive work on it and the potential energy decreases.

An ideal ammeter has A. zero resistance. It should be connected in parallel with the circuit element being measured. B. zero resistance. It should be connected in series with the circuit element being measured. C. infinite resistance. It should be connected in parallel with the circuit element being measured. D. infinite resistance. It should be connected in series with the circuit element being measured. E. none of the above.

B. zero resistance. It should be connected in series with the circuit element being measured.

Three pairs of conducting plates (capacitors) are shown in the figure below. Pair B has the same separation as pair A but twice the plate area. Pair C has the same area as pair A but half the separation between the plates. The insulating material between the plates of all capacitors is the same. Rank the pairs of plates according to their capacitance. C > A = B C > A > B C = B > A A = B = C B > A > C

C = B > A

What current flows from the battery in the circuit shown in the figure? The battery is ideal, and all the numbers are accurate to two significant figures. A) 3.0 A B) 0.35 A C) 2.0 A D) 2.5 A

C) 2.0 A

Thirteen resistors are connected across points A and B as shown in the figure. If all the resistors are accurate to 2 significant figures, what is the equivalent resistance between points A and B? A) 4.0 Ω B) 6.0 Ω C) 8.0 Ω D) 10 Ω E) 12 Ω

C) 8.0 Ω

The figure shows three electric charges labeled Q1, Q2, Q3, and some electric field lines in theregion surrounding the charges. What are the signs of the three charges? A) Q1 is negative, Q2 is positive, Q3 is negative. B) Q1 is positive, Q2 is positive, Q3 is negative. C) Q1 is positive, Q2 is negative, Q3 is positive. D) All three charges are negative. E) All three charges are positive.

C) Q1 is positive, Q2 is negative, Q3 is positive.

Which of the following statements is correct? A) Earth's north pole is the north pole of Earth's magnetic field B) Earth's south pole is the south pole of Earth's magnetic field C) The north pole of a magnet points towards Earth's north pole D) The north pole of a magnet points towards Earth's south pole E) none

C) The north pole of a magnet points towards Earth's north pole

When two or more capacitors are connected in parallel across a potential difference A) each capacitor carries the same amount of charge. B) the equivalent capacitance of the combination is less than the capacitance of any of the capacitors. C) the potential difference across each capacitor is the same. D) All of the above choices are correct. E) None of the above choices are correct.

C) the potential difference across each capacitor is the same.

If a bar magnet(S-N) is cut in half, you end up with

C. S-N, S-N

In the circuit shown in (a), the two bulbs A and B are identical. Bulb B is removed and the circuit is completed as shown in (b). Compared to the brightness of bulb A in (a), bulb A in (b) is A. just as bright. B. less bright. C. brighter. D. any of the above, depending on the rated wattage of the bulbs.

C. brighter.

In the circuit shown, the two bulbs A and B are identical. Compared to bulb A, A. bulb B glows more brightly. B. bulb B glows less brightly. C. bulb B glows equally brightly. D. the answer depends on whether the mobile charges in the wires are positively or negatively charged.E. the answer depends on whether the same kind of wire is used in all parts of the circuit.

C. bulb B glows equally brightly.

An ideal voltmeter has A. zero resistance. It should be connected in parallel with the circuit element being measured. B. zero resistance. It should be connected in series with the circuit element being measured. C. infinite resistance. It should be connected in parallel with the circuit element being measured. D. infinite resistance. It should be connected in series with the circuit element being measured. E. none of the above.

C. infinite resistance. It should be connected in parallel with the circuit element being measured.

Two point charges, +q and -q, are placed as shown. Rankthe five points labeled A, B, C, D, and E in order of the electric potential at each point due to the two point charges, from most positive to most negative. The five points and the two point charges all lie in the same plane. A. ABCDE B. EDCBA C. CADBE D. CDEBA

C.CADBE

A large, metallic, spherical shell has no net charge. It is supported on an insulating stand and has a small hole at the top. A small tack with charge Q is lowered on a silk thread through the hole into the interior of the shell. What is the charge on the inner surface of the shell? A) Q/2 B) 0 C) Q D) - Q

D) - Q

A negatively charged balloon is attracted to a neutral wooden cabinet due to polarization. Which one of the following diagrams best depict why this occurs? B E C A F D

D

Equipotential lines are shown. For which region is the magnitude of the electric field the greatest? C A D It is the same everywhere. B

D

Point P is 5 cm above the wire as you look straight down at it. In which direction is the magnetic field at P?

D down

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

D) trajectory Z

3 charges (equal magnitude are shown). What is the direction of the E-field at P? A. +x B. -x C. +y D. -y E. None of the above.

D. -y

Determine the power delivered by the battery A. 9 W B. 18 W C. 36 W D. 54 W

D. 54 W

Two small objects each with a net charge of Q exert a force of magnitude F on each other. We double the distance between these charges. What is the magnitude of the force? A. 16F B. 4F C. F D. F/4 E. None of the above

D. F/4

Three point charges lie at the vertices of an equilateral triangle as shown. All three charges have the same magnitude, but charges #1 and #2 are positive (+q) and charge #3 is negative (-q). The net electric force that charges #2 and #3 exert on charge #1 is in A. the +x-direction. B. the -x-direction. C. the +y-direction. D. the -y-direction. E. none of the above.

D. the -y-direction.

Three capacitors are connected as shown in the figure. What is the equivalent capacitance between points a and b? A) 7.1 μF B) 12 μF C) 8.0 μF D) 4.0 μF E) 1.7 μF

E) 1.7 μF

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

E) It remains the same.

Consider a spherical Gaussian surface of radius R centered at the origin. A charge Q is placed inside the sphere. To maximize the magnitude of the flux of the electric field through the Gaussian surface, the charge should be located A) at x = 0, y = 0, z = R/2. B) at x = 0, y = R/2, z = 0. C) at x = R/2, y = 0, z = 0. D) at the origin. E) The charge can be located anywhere, since flux does not depend on the position of the charge as long as it is inside the sphere.

E) The charge can be located anywhere, since flux does not depend on the position of the charge as long as it is inside the sphere.

The current through the 3 Ωresistor is A. 9 A B. 6 A C. 5 A D. 3 A E. 1 A

E. 1 A

A parallel combination of resistors has an equivalent (or effective) resistance of 2 Ω. Which one of the following is true? Each of the individual resistances is greater than 2 Ω. Each of the individual resistances is smaller than 2 Ω. The sum of the individual resistances is 2 Ω. The sum of the reciprocals of the individual resistances is 2 Ω.

Each of the individual resistances is greater than 2 Ω.

A positive charge is placed at one of 3 locations in a region where the electric field is uniform. Compare the magnitude F of the electric force on the charge at the different locations. F is greatest at location 3. F is the same at all locations, but not zero. F is zero at all locations. F is greatest at location 1. F is greatest at location 2.

F is the same at all locations, but not zero.

Charges Q1 and Q2 are situated as shown below. The electric field is zero at point P. What conclusions can be drawn about the charges Q1 and Q2? I. The magnitudes of Q1 and Q2 are equal. II. The magnitude of Q1 is greater than the magnitude of Q2. III. The magnitude of Q1 is less than the magnitude of Q2. IV. Q1 and Q2 have the same sign. V. Q1 and Q2 have different signs.

II and IV are correct.

Three resistors connected in series carry currents labeled I1, I2, I3, respectively. Which of the following expresses the value of the total current IT in the system made up of the three resistors? IT = I1 + I2 + I3 IT = I1 = I2 = I3 IT = (1/I1 + 1/I2 + 1/I3) IT = (1/I1 + 1/I2 + 1/I3)-1 IT = 3I1 = 3I2 = 3I3

IT = I1 = I2 = I3

Consider a uniform electric field, for example the field inside a parallel plate capacitor, as shown.If a proton is taken from location B to location C, how does its potential energy change? It decreases. It increases. It does not change.

It decreases.

Which of the following statements are true? (a) The electric field of a point charge always points away from the charge. (b) All macroscopic charges Q can be written as Q = ±Ne, where N is an integer and e is the charge of the electron. (c) Electric field lines never diverge from a point in space. (d) Electric field lines never cross at a point in space.

Only statements (b) and (d) are true.

Two negative point charges with the same charge -q and a point P are located as shown, at the vertices of an equilateral triangle. What is the direction of the electric field due to the two point charges at point P? The +y direction The field at point P is zero. The -x direction The +x direction The -y direction

The +x direction

Equipotential lines around several point charges are shown. What are the signs of the charges at points A and B? The charge at B is positive and the charge at A is negative. Both charges are positive. The charge at A is positive and the charge at B is negative. This cannot be determined fro the information on the diagram. Both charges are negative.

The charge at B is positive and the charge at A is negative.

Using the image below as your only evidence, what MUST be true about charged objects 1 and 2 below? Both objects have a negative charge. The charge on both objects has the same sign. Both objects have the same amount of charge. Both objects have a positive charge.

The charge on both objects has the same sign.

Assume the voltage across the ends of a wire is doubled. If the material obeys Ohm's law, which one of the following statements concerning the resistance of the wire is true? The resistance decreases by a factor of four. The resistance is twice its original value. The resistance increases by a factor of four. The resistance is not changed. The resistance is one half of its original value.

The resistance is not changed.

The electric field-line diagram visualizes the electric field produced by a pair of charges. A negative test charge is placed at point P directly between the two charges in the diagram. The test charge will accelerate towards the right.. The test charge will accelerate towards the left. The test charge will stay at rest at point P. The test charge will move on an equipotential line perpendicular to the field lines.

The test charge will accelerate towards the right..

The electric field-line diagram visualizes the electric field produced by a pair of charges. A negative test charge is placed at point P directly between the two charges in the diagram. The test charge will accelerate towards the right.. The test charge will stay at rest at point P. The test charge will accelerate towards the left. The test charge will move on an equipotential line perpendicular to the field lines.

The test charge will accelerate towards the right..

What is the direction of the Coulomb force on the charge pointed at by the arrow? (Charge is given in arbitrary units.) Down There is no direction, the net force is zero. Towards the left Towards the right Up

Towards the right

A positively charged particle moves in the positive z-direction. The magnetic force on the particle is in the positive y-direction. What can you conclude about the x-component of the magnetic field at the particle's position? a. Bx >0 b. Bx<0 c. Bx=0 d. neither a or b e. any of a b or c is possible

a. Bx >0

A long, thin bar magnet has a north pole at one end and a south at the other. If you break it in half, the two new ends will attract repel neither

attract

You wish to study a resistor in a circuit. To simultaneously measure the current in the resistor and the voltage across the resistor, you would place a. an ammeter in series and a voltmeter in series b. an ammeter in series and a voltmeter in parallel c. an ammeter in parallel and a voltmeter in series d. an ammeter in parallel and a voltmeter in parallel E none

b. an ammeter in series and a voltmeter in parallel

Two point charges +q and -q are arranged as shown. Through which closed surface is/are the net electric flux equal to zero? a b c d both c and d

both c and d

The electric field lines around an electric dipole are best represented by which, if any, of the diagrams in figure? (c) (a) none of the diagrams in the figure (d) (b)

d

An electron (|q| = 1.6*10-19 C, m = 9.1*10-31 kg) is suspended at rest in a uniform electric field of magnitude E. Its weight mg (g = 9.8 m/s2) near the Earth's surface is exactly canceled by the electrostatic force. The electric field points in a direction making an angle of 45o with the horizontal. in an arbitrary direction. The direction of the field makes no difference for this problem. in a horizontal direction, parallel to the surface of Earth. down. up.

down

Compared to the effective resistance of two resistors connected in series, the effective resistance of the same two resistors connected in parallel is lower. the same. either higher, lower, or the same, depending on the resistances of the individual resistors. higher.

lower

You have just pulled your clothes from the dryer and find that a sock is clinging to your jeans with static electricity. You pull the two apart. As the jeans and the sock move apart, the force between them becomes weaker because the electric current moving through each garment diminishes as they move apart. electric charge on each garment increases as they move apart. the force between the electric charges becomes weaker with increasing distance. the garments become polarized. electric charge on each garment diminishes as they move apart.

the force between the electric charges becomes weaker with increasing distance.

Which of the two arrangements shown has the smaller equivalent resistance between point a and b the series arrangement the parallel arrangement equivalent resistance for both answer depends on values of inidividual resistances

the parallel arrangement

Consider the equipotential surfaces shown. In this region of space what is the approximate direction of the electric field? out of page into page toward top toward bottom

toward bottom