PHYS 1401 Exam 1
b
A +4.0-μC and a -4.0-μC point charge are placed as shown in the figure. What is the potential difference between points A and B? a) 96 V b) 96 kV c) 0 V d) 48 kV
a
A 1.0-m length of nichrome wire has a radius of 0.50 mm and a resistivity of 1.0 × 10-6 Ω • m. When this wire carries a current of 0.50 A, what is the voltage across its ends? a) 0.64 V b) 0.32 V c) 0.0030 V d) 1.6 V
a
A 100-W driveway light bulb is on 10 hours per day. If the power company charges 10¢ for each kilowatt-hour of electricity used, estimate the yearly cost to operate the bulb if it is used every day for a 365-day year. a) $37 b) $73 c) $3.65 d) $7.30
b
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 m d) 0.65 cm
b
A 150-W light bulb is designed to operate at 110 V dc. How much current does it draw? a) 0.73 A b) 1.4 A c) 15 A d) 2.0 A
d
A 22-A current flows into a parallel combination of 4.0-Ω, 6.0-Ω, and 12-Ω resistors. What current flows through the 12-Ω resistor? a) 7.3 A b) 18 A c) 11 A d) 3.7 A
d
A 4.0-g bead carries a charge of 20 μC. The bead is accelerated from rest through a potential difference V, and afterward the bead is moving at 2.0 m/s. What is the magnitude of the potential difference V? a) 800 V b)400 kV c) 800 kV d) 400 V
a
A 5-µF, a 7-µF, and an unknown capacitor CX are connected in parallel between points a and b as shown in the figure. What do you know about the equivalent capacitance Cab between a and b? a) Cab > CX b) Cab < CX c) Cab > 12 µF d) 5 µF < Cab < 12 µF
d
A 5.0-μF, a 14-μF, and a capacitor are connected in parallel. How much capacitance would a single capacitor need to have to replace the three capacitors? a) 5 uF b) 21 uF c) 14 uF d) 40 uF
d
A battery has an emf ε = 43.0 V and an internal resistance r = 8.0 Ω, as shown in the figure. When the terminal voltage Vab is equal to 34.0 V, the current through the battery, including its direction, is closest to a) 5.4 A, from b to a. b) 4.2 A, from a to b c) 4.2 A, from b to a d) 1.1 A, from b to a.
a
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) 6000 V/m b) 600 V/m c) zero d) 6.0 V/m
a
A battery you buy at the store has an internal emf of 3.0 V. If it has an internal resistance ofwhat current will this battery put out if it is short-circuited? a) 0.21 A b) 42 A c) 130 A d) 4.7 A
a
A certain 20-A circuit breaker trips when the current in it equals 20 A. What is the maximum number of 100-W light bulbs you can connect in parallel in an ideal 120-V dc circuit without tripping this circuit breaker? a) 23 b) 27 c) 11 d) 17
c
A combination of a 2.0-Ω resistor in series with 4.0-Ω resistor is connected in parallel with a 3.0-Ω resistor. What is the equivalent resistance of this system? a) 3.0 Ω b) 9.0 Ω c) 2.0 Ω d) 4.0 Ω
d
A dielectric material such as paper is inserted between the plates of a capacitor as the capacitor holds a fixed charge on its plates. What happens to the electric field between the plates as the dielectric is inserted? a) The field reduces to zero b) there is no change in the field c) the field becomes stronger d) the field becomes weaker
b
A galvanometer can be converted to an ammeter by the addition of a a) large resistance in parallel b) small resistance in parallel c) small resistance in series d) large resistance in series
d
A light bulb operating at 110 V draws 1.40 A of current. What is its resistance? a) 154 Ω b) 12.7 Ω c) 109 Ω d) 78.6 Ω
c
A metal sphere of radius 10 cm carries an excess charge of +2.0 μC. What is the magnitude of the electric field 5.0 cm above the sphere's surface? a) 4.0 x 10^7 N/C b) 4.0 x 10^5 N/C c) 8.0 x 10^5 N/C d) 8.0 x 10^7 N/C e) 4.0 x 10^9 N/C
c
A network of capacitors is mostly inside a sealed box, but one capacitor CX is sticking out, as shown in the figure. When you connect a multimeter across points a and b, it reads 27.0 µF. What is CX? a) 27.0 µF b) 2.4 µF c) 4.0 µF d) 2.2 µF
d
A number of resistors are connected across points A and B as shown in the figure. What is the equivalent resistance between points A and B? a) 6 Ω b) 10 Ω c) 4 Ω d) 8 Ω
c
A parallel-plate capacitor is connected to a battery and becomes fully charged. The capacitor is then disconnected, and the separation between the plates is increased in such a way that no charge leaks off. As the plates are being separated, the energy stored in this capacitor a) does not change b) become zero c) increases d) decreases
d
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 × 10^4 N/C b) 8.2 × 10^4 N/C c) 5.1 × 10^4 N/C d) 1.2 × 10^4 N/C
b
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) 2vo b) vo sqrt2 c) 4vo d) 8vo
b
A resistor, an uncharged capacitor, a dc voltage source, and an open switch are all connected in series. The switch is closed at time t = 0 s. Which one of the following is a correct statement about the circuit? a) The capacitor charges to its maximum value in one time constant b) Once the capacitor is essentially fully charged, there is no current in the circuit c) Current flows through the circuit even after the capacitor is essentially fully charged d) The potential difference across the resistor is always equal to the potential difference across the capacitor.
b
A resistor, an uncharged capacitor, a dc voltage source, and an open switch are all connected in series. The switch is closed at time t = 0 s. Which one of the following is a correct statement about this circuit? a) The voltage on the capacitor after one time constant is 1/e of the maximum value b) The charge on the capacitor after four time constants is about 98% of the maximum value c) The charge on the capacitor after one time constant is 1/e of its maximum value d) The charge on the capacitor after one time constant is 50% of its maximum value.
b
A small 0.050-kg insulating sphere carries a charge of -60 μC and is hanging by a vertical silk thread from a fixed point in the ceiling. An external uniform vertical electric field is now applied. If the applied electric field has a magnitude of 3000 N/C and is directed downward, what is the tension in the silk thread? a) 0.71 N b) 0.31 N c) 0.41 N d) 0.19 N
b
A small 4.0-µC charge and a small 1.5-µC charge are initially very far apart. How much work does it take to bring them to a final configuration in which the 4.0-µC charge is at the point x = 1.0 mm, y = 1.0 mm, and the 1.5-µC charge is at the point x = 1.0 mm, y = 3.0 mm? a) 13.5 J b) 27 J c) 13.5 kJ d) 54 J
a
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 x10^4 N/C b) 8.5 X10^-7 N/C c) 8.5 X10^2 N/C d) 8.1 X 10^-5 N/C
c
A sphere with radius 2.0 mm carries a + 2 charge. What is the potential difference, between point B, which is 4m from the center of the sphere, and point A, which is 6m from the center of the sphere? a) 170 V b) -0.63 V c) 1500 V d) -1500 V
d
A total of 2.0 × 1013 electrons pass a given point in a wire in 15 s. What is the current in the wire? a) 1.3 mA b) 3.2 uA c) 1.3 A d) 0.21 uA
b
A tube of mercury with resistivity 9.84 × 10-7 Ω • m has a uniform electric field of 23 N/C inside the mercury. How much current is flowing in the tube, if the radius of the tube is 0.495 mm? a) 29 A b) 18 A c) 180 A d) 280 A
b
After a proton with an initial speed of 1.50 × 105 m/s has increased its speed by accelerating through a potential difference of 0.100 kV, what is its final speed? a) 8.80 × 10^5 m/s b) 2.04 × 10^5 m/s c) 4.56 × 10^5 m/s d) 1.55 × 10^6 m/s
d
An ideal air-filled parallel plate capacitor with plate a separation of 4.0 cm has a plate area of 0.040 m2. What is the capacitance of this capacitor with air between these plates? a) 8.9 uF b) 89 uF c) 8.9 nF d) 8.9 pF
b
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/2 b) 4C c) C/4 d) 2C
d
An ideal parallel-plate capacitor having circular plates of diameter D that are a distance d apart stores energy U when it is connected across a fixed potential difference. If you want to triple the amount of energy stored in this capacitor by changing only the size of its plates, the diameter should be changed to a) 9D b) D/sqrt3 c) 3D d) Dsqrt3
d
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.
b
As more resistors are added in series to a constant voltage source, the power supplied by the source a) increases for a time and then starts to decrease b) decreases c) does not change d) increases
d
At a distance d from a point charge Q, the energy density in its electric field is u. If we now go to a distance d/2 from the charge, what is the energy density at the new location? a) 4u b) 8u c) 2u d) 16u
d
Consider two copper wires with circular cross-sections and equal lengths. One wire has 3 times the diameter of the other. How do the resistances of these two wires compare? a) The thicker wire has 9 times the resistance of the thinner wire b) The thicker wire has 1/3 the resistance of the thinner wire c) The thicker wire has 3 times the resistance of the thinner wire d) The thicker wire has 1/9 the resistance of the thinner wire.
c
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 half that of wire #2 b) The resistance of wire #1 is four times higher than that of wire #2 c) The resistance of wire #1 is twice as high as that of wire #2 d) The resistance of wire #1 is equal to that of wire #2.
false
Electrically neutral objects cannot exert an electrical force on each other, but they can exert a gravitational force on each other. (true/false)
a
For the graph shown in the figure, what physical quantity does the slope of the graph represent for ohmic material? a) current b) 1/current c) resistivity d) power
b
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) negative b) zero c) positive d) impossible to determine based on the information given
a
Four point charges of varying magnitude and sign are arranged on 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 point charge with a charge +Q? a) A b) B c) C d) D
d
Four unequal resistors are connected in series with each other. Which one of the following statements is correct about this combination? a) the equivalent resistance is less than that of the smallest resistor b) the equivalent resistance is equal to average of the four resistances c) the equivalent resistance is more than the largest resistance d) the equivalent resistance is equal to that of any one of the resistors
a
How many electrons are necessary to produce 1.0 C of negative charge? a) 6.3 x10^18 b) 6.0 x 10^23 c) 1.6 x 10^19 d) 6.3 x 10^9
b
How much current will be flowing through a length of copper wire with radius if it is connected to a source supplying The resistivity of the metal is 1.68 × 10-8 Ω • m. a) 1 nA b) 0 A c) 5 A d) 8 A
d
Identical light bulbs can be attached to identical ideal batteries in three different ways (A, B, or C), as shown in the figure. The ranking (from lowest to highest) of the total power produced by the battery is a) A, C, B b) C, B, A c) C, A, B d) B, A, C
a
If a quantity you calculated has units of A • s, what is that quantity? a) charge b) capacitance c) resistance d) potential
d
If a quantity you calculated has units of kg x m^2/ s^2 x C, what is that quantity? a) resistance b) resistivity c) charge d) potential
b
If an electron is accelerated from rest through a potential difference of 1500 V, what speed does it reach? a) 1.5 × 10^7 m/s b) 2.3 × 10^7 m/s c) 1.9 × 10^7 m/s d) 1.1 × 10^7 m/s
b
If the result of your calculation of a quantity has SI units kg • m2/(s2 • C), that quantity could be a) a capacitance b) an electric potential difference c) an electric field strength d) an electric potential energy.
d
If the result of your calculations for a quantity has SI units of C2 • s2/(kg • m2), that quantity could be a) a dielectric constant b) an electric potential difference c) an electric potential energy d) a capacitance
c
If the voltage across a circuit of constant resistance is doubled, the power dissipated by that circuit will a) decrease to one-half the original power b) decrease to one-fourth the original power c) be four times as large d) be two times as large.
a
In an electroplating process, it is desired to deposit 40 mg of silver on a metal part by using a current of 2.0 A. How long must the current be allowed to run to deposit this much silver? The silver ions are singly charged, and the atomic mass of silver is 108 g/mol. a) 18 s b) 16 s c) 20 s d) 22 s
d
In outer space, a positive charge q is released near a positive fixed charge Q, as shown in the figure. As q moves away from Q, what is true about the motion of q? a) It will move with constant acceleration b) It will move with increasing acceleration c) It will move with increasing speed d) It will move with decreasing acceleration.
a
Over ordinary temperature ranges, the resistance of most metals such as copper a) increases as the metal gets hotter b) is a maximum at 20°C c) is independent of the temperature of the metal d) decreases as the metal gets hotter
a
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? a) -16 nC b) 17 nC c) 16 nC d) -17 nC
d
The figure shows a graph of the power dissipated in a resistor as a function of the resistance. What quantity does the slope of this graph represent? a) the potential difference across the resistor b) the current in the resistor c) the resistivity of the resistor d) the square of the current in the resistor
d
The figure shows two tiny 5.0-g spheres suspended from very light 1.0-m-long threads. The spheres repel each other after each one is given the same positive charge and hang at rest when θ = 4.1°. What is the charge on each sphere? a) 360 nC b) 180 nC c) 22 nC d) 89 nC
a
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
b
The lamps in a string of decorative lights are connected in parallel across a constant-voltage power source. What happens if one lamp burns out? (Assume negligible resistance in the wires leading to the lamps.) a) the other lamps get brighter equally b) the brightness of the lamps will not change appreciably c) the other lamps get brighter, but some get brighter than others d) the other lamps get dimmer equally
b
The length of a certain wire is doubled while its radius is kept constant. What is the new resistance of this wire? a) It is 4 times as large b) It is 2 times as large c) It stays the same d) It is 3 times as large.
b
The network shown is assembled with uncharged capacitors X , Y, and Z, with and The switches S1 and S2 are initially open, and a potential difference Vab = 120 V is applied between points a and b. After the network is assembled, switch S1 is then closed, but switch S2 is kept open. How much charge is finally stored in capacitor Y? a) 140 µC b) 110 µC c) 81 µC d) 54 µC
d
The resistivity of the material of a wire is 1.76 × 10-8 Ω • m. If the diameter of the wire is 2.00 mm and its length is 2.00 m, what is its resistance? a) 0.112 Ω b) 11.2 Ω c) 112 Ω d) 0.0112 Ω
c
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 x component of the electrostatic force on the -9.0 μC charge due to the other two charges? a) -0.41 N b) 0.55 N c) 0.41 N d) 0.64 N
a
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. a) 0 V b) 1300 V c) 1900 V d) 640 V
d
The zirconium nucleus contains 40 protons, and an electron is 1.0 nm from the nucleus. What is the electric force on the electron due to the nucleus? a) 6.8 nN b) 2.9 nN c) 1000 C d) 9.2 nN
c
Three 2.0-Ω resistors are connected to form the sides of an equilateral triangle ABC as shown in the figure. What is the equivalent resistance between any two points, AB, BC, or AC, of this circuit? a) 2.0 Ω b) 6.0 Ω c) 1.3 Ω d) 3.3 Ω
b
Three capacitors are arranged as shown in the figure, with a voltage source connected across the combination. C1 has a capacitance of 9.0 pF, C2has a capacitance of 18 pF and C3 has a capacitance of 27 pF Find the potential drop across the entire arrangement if the potential drop across C2 is 257 V a) 1000 V b) 1500 V c) 430 V d) 200 V
c
Three equal negative point charges -q 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 center of the square? a) A b) B c) C d) D
a
Three equal positive point charges +q 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 B C D
d
Three identical capacitors are connected in parallel to a potential source (battery). If a charge of Q flows into this combination, how much charge does each capacitor carry? a) 3Q b) Q/9 c) Q d) Q/3
d
Two 5.0-µC point charges are 12 cm apart. What is the electric potential (relative to infinity) of this combination at the point where the electric field due to these charges is zero? a) 25 MV b) 0 MV c) 12.5 MV d) 1.5 MV
b
Two capacitors are connected as shown in the figure, with C1 = 4.0 µF and C2 = 7.0 µF. If a voltage source V = 90 V is applied across the combination, find the potential difference across C1. a) 36 V b) 57 V c) 60 V d) 9 V
c
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? a) 75 nC b) 95 nC c) 140 nV d) 120 nC
a
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) 1/16 N b) 1/4 N c) 1/8 N d) 2N
b
Two point charges of +2.00 μC and +4.00 μC are at the origin and at the point x = 0.000 m, y = -0.300 m, as shown in the figure. What is the electric potential due to these charges, relative to infinity, at the point P at x = 0.400 m on the x-axis? a) 15.7 kV b) 117 kV c) 36 kV d) 11.7 kV
a
Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are halved and their separation is also halved, what happens to the electrical force that each charge exerts on the other one? a) It remains the same b) it increases by a factor of 4 c) It increases by a factor of 8 d) It increases by a factor of 2.
d
Two protons are released from rest, with only the electrostatic force acting. Which of the following statements must be true about them as they move apart? a) Their acceleration keeps decreasing b) Their kinetic energy keeps decreasing c) Their electric potential energy keeps increasing d) Their electric potential energy keeps decreasing.
c
Two resistors having resistances of 5.0 Ω and 9.0 Ω are connected in parallel. A 4.0-Ω resistor is then connected in series with the parallel combination. An ideal 6.0-V battery is then connected across the series-parallel combination. What is the current through the 9.0-Ω resistor? a) 0.67 A b) 0.83 A c) 0.30 A d) 0.35 A
a
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 magnitude of q1 is less than the magnitude of q2 b) q1 and q2 have the same sign; the magnitudes are equal c) q1 is negative and q2 is positive; the magnitudes are equal d) q1 and q2 have the same sign; the magnitude of q1 is greater than the magnitude of q2.
d
Two tiny beads, each of mass 3.2 g, carry equal-magnitude charges. When they are placed 6.4 cm apart and released in outer space, they begin to accelerate toward each other at 538 m/s2. What is the magnitude of the charge on each bead? a) 44 nC b) 1800 nC c) 1300 nC d) 890 nC
a
Two tiny grains of sand having charges of 4.0 μC and -4.0 μC are situated along the x-axis at x1 = 2.0 m and x2 = -2.0 m. What is electric potential energy of these grains relative to infinity? a) -36 mJ b) 36 mJ c) -72 mJ d) 0 J
a
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. a) 1.08 × 10^5 V b) 0.00 V c) 5.40 × 10^4 V d) 2.70 × 10^4 V
b
What current is flowing in a wire if 0.67 C of charge pass a point in the wire in 0.30 s? a) 0.67 A b) 2.2 A c) 0.30 A d) 0.20 A
a
What is the charge on 1.0 kg of protons? a) 9.6 × 10^7 C b) 1000 C c) 6.0 × 10^26 C d) 1.0 C
b
What is the equivalent resistance in the circuit shown in the figure? a) 55 Ω b) 50 Ω c) 35 Ω d) 80 Ω
c
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? a) 7.8 × 10^5 N/C b) 1.5 × 10^6 N/C c) 6.9 × 10^6 N/C d) 2.1 × 10^6 N/C
d
What is the resistance of 1.0 m of a solid cylindrical metal cable having a diameter of 0.40 inches and a resistivity of 1.68 × 10-8 Ω • m? a) 0.0021 Ω b) 0.0012 Ω c) 0.00012 Ω d) 0.00021 Ω
a
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? a) 25 nC b) 0.025 C c) 1.0 C d) 25 C
c
When a current flows through a metal wire, the moving charges are a) postive metal ions b) negative metal ions c) only electrons d) only protons
c
When a current flows through an ionic liquid such as salty water, the moving charges are a) only electrons b) only protons c) both positive and negative ions d) only negative ions
c
When a dielectric material is introduced between the plates of a parallel-plate capacitor and completely fills the space, the capacitance increases by a factor of 4. What is the dielectric constant of the material that was introduced? a) 2 b) 1/4 c) 4 d) 0.4
d
When current is flowing in an ordinary metal wire, the magnitude of the average velocity of the electrons is closest to a) 1 km/s b) the speed of light c) 10 m/s d) 1 mm/s
c
When two or more different capacitors are connected in series across a potential source, which of the following statements must be true? a) The equivalent capacitance of the combination is less than the capacitance of any of the capacitors b) The potential difference across each capacitor is the same c) Each capacitor carries the same amount of charge d) The total voltage across the combination is the algebraic sum of the voltages across the individual capacitors.
d
Which one of the following quantities is equivalent to 1 Ω? a) 1 A s b) 1 V a c) 1 W/A d) 1 V/A
d
X and Y are two initially uncharged metal spheres on insulating stands, and they are in contact with each other. A positively charged rod R is brought close to X as shown in part (a) of the figure. Sphere Y 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) Both X and Y are negative c) Both X and Y are neutral d) X is negative and Y is positive.
c
You buy a AA battery in the store, and it is marked 1.5 V. If this marking is strictly accurate, while this battery is fresh a) its terminal voltage will be more than 1.5 V when it is used in a circuit b) its terminal voltage will be 1.5 V when it is used in a circuit c) its terminal voltage will be less than 1.5 V when it is used in a circuit.
c
as shown in the figure, three charges are at the vertices of an equilateral triangle. The charge Q is 6.7 nC, and all the other quantities are accurate to two significant figures. What is the magnitude of the net electric force on the charge Q due to the other two charges? a 1.4 x 10^-3 N b) 1.2 x 10^-3 N c) 2.1 x 10^-3 N d) 1.0 x 10^-3 N
