PH 106 Final
Unpolarized light with intensity S is incident on a series of polarizing sheets. The first sheet has its transmission axis oriented at 0°. A second polarizer has its transmission axis oriented at 45° and a third polarizer oriented with its axis at 90°. Determine the fraction of light intensity exiting the third sheet with and without the second sheet present.
.25S, 0
Horizontally polarized light of intensity S is incident on a polarizer with its transmission axis oriented at 45°. Determine the fraction of light intensity exiting the polarizer.
.5S
A permanent magnet is moved toward a 320-turn solenoid such that the magnetic field inside the solenoid increases from zero to 0.50 T in 0.75 s. The radius of the solenoid is 0.035 m. The ends of the solenoid are connected in series with a light bulb. What emf is induced during this time interval?
.82 V
When horizontally polarized light is incident on a sheet of polarizing material with a transmission axis oriented vertically, what percentage of the light is transmitted through the material?
0%
Two 20-Ω resistors are connected in series. A potential difference of 9 V is then applied across the resistors. What is the resulting current through the resistors?
0.23 A
Two 20-Ω resistors are connected in parallel. A potential difference of 9 V is then applied across both resistors. What is the resulting total current through the two resistors?
0.90 A
A magnetic dipole has two stable orientations in a magnetic field. At what two angles relative to the magnetic field direction are these orientations?
0º and 180º
At one point during a rain storm, the rain is falling at a constant rate of n drops per square meter at an angle of 60° with respect to the horizontal direction. Unfortunately Ted has left three windows open: (1) the sunroof on his car that measures 0.6 m by 0.3 m, (2) his bathroom window that measures 0.6 m by 0.2 m; and (3) his bedroom window that measures 0.6 m by 0.3 m. The bedroom and bathroom windows are perpendicular to the ground and the sunroof is parallel to the ground. Which of the window openings has the greatest flux?
1
What is the direction of the magnetic field at the point P, directly below a point at the center of the magnet? The numbered arrows represent various directions. Direction "1" is to the right, "2" to the left, "3" is upward, "4" is downward, and "5" is toward you.
1
In analyzing electric circuits containing a battery and at least one resistor, what is the change in potential across a resistor as one moves through it in the direction of the current?
-IR
A balloon has an initial radius of 0.075 m. A circle is painted on the balloon using silver metal paint. When the paint dries, the circle is a very good electrical conductor. With the balloon oriented such that a 1.5-T magnetic field is oriented perpendicular to the plane of the circle, air is blown into the balloon so that it expands uniformly. The silver circle expands to a radius 0.125 m in 1.5 s. Determine the induced emf for this silver circle during this period of expansion.
.031 V
An inductor circuit operates at a frequency f = 120 Hz. The peak voltage is 120 V; and the peak current through the inductor is 2.0 A. What is the inductance of the inductor in the circuit?
.080 H
A 150-Ω resistor and a 0.80-mH inductor are used in an LR circuit. If the initial current in the circuit is 2.0 A when a switch is thrown that allows the current in the circuit to decay, at what time will the current be 1.0 A?
.083 s
Consider the following quantities: (1) mass, (2) velocity, (3) charge, and (4) magnetic field strength. Upon which of these quantities is the force on a charged particle moving in a magnetic field dependent?
2, 3, and 4 only
The resistance in an RC circuit is comprised of a 1.5-MΩ resistor in parallel with a 2.0-MΩ resistor. What is the time constant for this circuit if the capacitance is 2.5 μF?
2.0 s
What is the magnitude of the electrostatic force that two electrons separated by 1.0 nm exert on each other?
2.3 x 10⁻¹⁰ N
A total charge of -6.50 μC is uniformly distributed within a sphere that has a radius of 0.150 m. What is the magnitude and direction of the electric field at 0.300 m from the surface of the sphere?
2.89 x 10⁵ N/C, radially inward
A capacitor has a very large capacitance of 10 F. The capacitor is charged by placing a potential difference of 2 V between its plates. How much energy is stored in the capacitor?
20 J
When unpolarized light is incident on a sheet of polarizing material with a transmission axis oriented vertically, what percentage of the light is transmitted through the material?
50%
Points P and Q are separated by a distance of 0.10 m in a uniform electric field. The potential difference between points P and Q is 55 V. What is the magnitude of the electric field?
550 V/m
The ac adapter for a laptop computer contains a transformer. The input of the adapter is the 120 volts from the ac wall outlet. The output from the transformer is 20 volts. What is the turns ratio of the transformer?
6
When a potential difference is applied to a certain copper wire, a current of 1.5 A passes through the wire. If the wire was removed from the circuit and replaced with a copper wire of twice the diameter, what current would flow through the new wire? Assume the wires are identical in all other aspects.
6.0 A
The battery capacity of a lithium ion battery in a digital music player is 750 mA-h. The manufacturer claims that the player can operate for eight hours if the battery is initially fully charged. Given this information, determine the number of electrons that flow through the player as you listen to your favorite songs for three hours.
6.3 x 10²¹ electrons
Which of the following choices correctly indicates the relationship between the magnetic field due to a current carrying, long straight wire at a distance R from the wire?
B α 1/R
In which one of the following situations does a conventional electric current flow due north?
Electrons in a beam are moving due south.
Which one of the following statements concerning emf is true?
Emf is the work done in moving a single charge from one terminal to the other of an emf device.
Consider the two charges shown in the drawing. Which of the following statements correctly describes the direction of the electric force acting on the two charges? q₁=+3.2µC q₂=-1.6µC
The force on q₁ points to the right and the force on q₂ points to the left.
Through a certain cross-sectional area of a wire, one coulomb of electrons pass each second. In this case, the current through the wire is equal to which one of the following choices?
one ampere
Two point charges are stationary and separated by a distance R. Which one of the following pairs of charges would result in the largest repulsive force? -2q and +4q -3q and -2q +3q and -2q +2q and +4q -3q and -q
+2q and +4q
Two point charges lie along the x axis. One charge, located at the origin, has a magnitude +2q. The other charge of unknown magnitude and sign is located at x = 5 units. If the electric potential at x = 4 units is equal to zero volts, what is the magnitude and sign of the second point charge?
+q/2
In analyzing electric circuits containing an ideal emf device that has an emf ε and at least one resistor, what is the change in potential across the emf device as one moves through it in the direction of the emf arrow?
+ε
Imagine a closed Gaussian surface and a particle that has a net charge q. Consider the following two statements: (1) "If the particle is enclosed by the surface the net electric flux through the surface cannot be equal to zero N/C." and (2) "If the particle is near the closed Gaussian surface, but outside of it, the net electric flux through the surface must be equal to zero N/C." Which of these two statements is true, if either?
1 and 2
How much charge is on the plates of a 11-μF capacitor that has been connected to a 120 V dc power supply for a long time?
1.3 x 10⁻³ C
At a distance of one centimeter from an electron, the electric field strength has a value E. At what distance is the electric field strength equal to E/2?
1.4 cm
The drift speed within a certain conductor is 0.10 mm/s. How many electrons move through a unit cross-sectional area in the circuit each second if the current is 2.5 A?
1.6 x 10²³
Consider the circuit shown. If the ideal emf in the circuit is 24 V and the three resistances are R1 = 2.5 Ω, R2 = 4.0 Ω, and R3 = 6.0 Ω, determine the current in the 4.0 Ω resistor. (3 resistors connected in series)
1.9 A
Which of the following expressions gives the energy density between the plates of a parallel plate capacitor?
1/2(ε₀)(V²/d²)
The electric potential of an uncharged, spherical conductor with a radius of 0.1 m is 10 V. If the sphere is located in a region of space with no electric fields, what is the electric potential at a point located 2 m from the center of the sphere?
10 V
When vertically polarized light is incident on a sheet of polarizing material with a transmission axis oriented vertically, what percentage of the light is transmitted through the material?
100%
An automatic coffee maker uses a resistive heating element to boil the 2.4 kg of water that was poured into it at 21 °C. The current delivered to the coffee pot is 8.5 A when it is plugged into a 120 V electrical outlet. If the specific heat capacity of water is 4186 J/kgC°, approximately how long does it take to boil all of the water?
13 minutes
At what orientation angle relative to the magnetic field direction does the magnetic potential energy of a magnetic dipole have its largest value?
180º
The drawing shows four points surrounding an electric dipole. Which one of the following expressions best ranks the electric potential at these four locations? (1) (4) P (2) (3)
1>2=4>3
A wire is used as a heating element that has a resistance that is fairly independent of its temperature within its operating range. When a current I flows through the wire, the energy delivered by the heater each minute is E. For what amount of current will the energy delivered by the heater each minute be 4E?
2I
Two identical resistors are connected in series across the terminals of a battery with a voltage V and a current I flows through the circuit. If one of the resistors is removed from the circuit and the remaining one connected across the terminals of the battery, how much current would flow through the circuit?
2I
A parallel plate capacitor with plates of area A and plate separation d is charged so that the potential difference between its plates is V. If the capacitor is then isolated and its plate separation is increased to 2d, what is the potential difference between the plates?
2V
The drawing shows two long, thin wires that carry currents in the positive z direction. Both wires are parallel to the z axis. The 50-A wire is in the x-z plane and is 5 m from the z axis. The 40-A wire is in the y-z plane and is 4 m from the z axis. What is the magnitude of the magnetic field at the origin?
3 x 10⁻⁶ T
When a potential difference is applied to a certain copper wire, a current of 1.5 A passes through the wire. If the wire was removed from the circuit and replaced with a copper wire of twice the cross- sectional area, what current would flow through the new wire? Assume the wires are identical in all other aspects.
3.0 A
Using Gauss' law, find the approximate magnitude of the electric field at the surface of a cube that has 0.10-m sides and a uniform volume charge density ρ = 2.0 × 10−9 C/m3.
3.77 N/C
Three parallel plate capacitors, each having a capacitance of 1.0 μF are connected in series. The potential difference across the combination is 100 V. What is the charge on any one of the capacitors?
33 µC
One end of resistor A is connected to the positive terminal of a battery and the other end is connected to resistor B. The opposite end of resistor B is connected to the negative terminal of the battery. If resistor A has resistance R and B has a resistance 2R, what is the equivalent resistance of this circuit?
3R
The manufacturer of a new laser claims that with only two standard AA batteries (together: 3.0 V, 20 kJ energy storage) that the product life is 25 hours. What is the approximate resistance in the laser's electrical circuitry?
40 Ω
A 150-μF capacitor is fully-charged when it has 6.1 × 10−3 C on its plates. What is the potential difference across the plates of the capacitor?
41 V
Two objects separated by a distance r are each carrying a charge −q. The magnitude of the force exerted on the second object by the first is F. If the first object is removed and replaced with an identical object that carries a charge +4q, what is the magnitude of the electric force on the second object?
4F
Four point charges are individually brought from infinity and placed at the corners of a square as shown in the figure. Each charge has the identical value +Q. The length of the diagonal of the square is 2a. What is the electric potential at the center of the square?
4kQ/a
Ernest O. Lawrence, of the University of California, Berkeley, invented the cyclotron in 1929. A more modern version was completed in 1961 at the Lawrence-Livermore Laboratory that has a radius of 88 inches. What is the frequency of circular motion at the "88-incher" if protons are circulating in a magnetic field of 0.48 T?
7.3 x 10⁶ Hz
Two solenoids, A and B, have the same length and cross-sectional area. Solenoid B has three times the number of turns per unit length. What is the ratio of the self-inductance of solenoid B to that of solenoid A?
9
A solenoid of length 0.250 m and radius 0.0200 m is comprised of 120 turns of wire. Determine the magnitude of the magnetic field at the center of the solenoid when it carries a current of 15.0 A.
9.05 x 10⁻³ T
A single circular loop of wire with radius 0.020 m carries a current of 8.0 A is placed at the center of a solenoid that has length 0.65 m, radius 0.080 m, and 1400 turns. Determine the value of the current in the solenoid so that the magnetic field at the center of the loop is zero tesla.
9.3 x 10⁻² A
At what orientation angle relative to the magnetic field direction does the torque of a magnetic dipole have its largest value?
90º
What is the angle of refraction when the angle of incidence is equal to the critical angle?
90º
Three identical conducting spheres on individual insulating stands are initially electrically neutral. The three spheres are arranged so that they are in a line and touching as shown. A negatively-charged conducting rod is brought into contact with sphere A. Subsequently, someone takes sphere C away. Then, someone takes sphere B away. Finally, the rod is taken away. What is the sign of the final charge, if any, of the three spheres?
A -, B-, C-
Three insulating balls are hung from a wooden rod using thread. The three balls are then individually charged via induction. Subsequently, balls A and B are observed to attract each other, while ball C is repelled by ball B. Which one of the following statements concerning this situation is correct?
A and B are charged with charges of opposite signs and C is the same sign as B; A is neutral and C is the same sign as B
What is the primary difference between an ideal emf device and a real emf device?
A real emf device has an internal resistance, but an ideal emf device does not.
Consider what would happen if electric field lines could cross each other. What would it mean if two electric field lines were to cross?
A test charge placed at the intersection of 2 electric fields would experience a net force in 2 different directions at once.
In which one of the following cases does the radiation pressure have the largest value?
All of the electromagnetic waves directed toward an object are reflected by it.
Which one of the following statements is not a characteristic of a voltmeter?
An ideal voltmeter has almost no resistance.
Which scientist is credited with assigning the "−" and "+" signs used to describe the two kinds of charge?
Benjamin Franklin
Two parallel wires have currents that have the same direction, but differing magnitude. The current in wire A is i; and the current in wire B is 2i. Which one of the following statements concerning this situation is true?
Both wires attract each other with the same amount of force.
Two parallel wires have currents that are in opposite directions and have differing magnitudes. The current in wire A is i; and the current in wire B is 2i. Which one of the following statements concerning this situation is true?
Both wires repel each other with the same amount of force.
In analyzing circuits in which resistors are wired partially in series and partially in parallel, which one of the following statements describes the preferred approach to take to determine the equivalent resistance in the circuit?
Break the circuit into smaller parts and find an equivalent resistance for each part. Then continue this process until all of the parts are added together correctly either in series or parallel until a single equivalent resistance is found.
The plates of an isolated parallel plate capacitor with a capacitance C carry a charge Q. What is the capacitance of the capacitor if the charge is increased to 4Q?
C
Electromagnetic waves have linear momentum as well as energy. What does this imply about electromagnetic waves?
Electromagnetic waves can exert pressure on an object.
The unit of electrical current is the ampere (A). Which one of the combinations of units is equivalent to the ampere?
C/s
What corresponds to the units for current?
C/s
Consider the following observations: (1) electric field lines are drawn connecting two point charges labeled A and B, (2) charge A is due north of charge B, and (3) a proton placed at the mid-point on a line connecting the two point charges travels due south. Which one of the following statements correctly indicates the signs of the two charges?
Charge A is positive and charge B is negative.
Why is an electrostatic force considered a conservative force?
Charged particles do not experience friction, which is a non-conservative force. The work required to move a charged particle from one point to another does not depend upon the path taken.
Which of the following laws or principles can be derived from Gauss' law?
Coulomb's law
Consider the situation shown in the drawing. A conducting loop is connected to a resistor. The resistor and loop are at rest in a magnetic field that is directed toward you. Within a short period of time the magnetic field is reduced to one half of its initial value. Which one of the following statements concerning an induced current, if any, in the loop is true?
During the time the magnetic field is decreasing, a current is induced that is directed counterclockwise around the loop.
Which one of the following expressions gives the correct relationship between the electric field strength E and the distance r from an electric dipole?
E α 1/r³
Consider the drawing which shows a uniform ring of charge of radius R. Which of the following expressions gives the correct dependence of the electric field at point P located on the z axis, where z >> R?
E α 1/z²
Consider a line of charge of length L that has a linear charge density λ that is located on the x axis beginning at x = d. Which one of the following expressions allows one to calculate the electric field at the origin?
E= λ/4πε₀ ∫d+L,d, dx/x²
A uniformly charged rod with a linear charge density λ is located along the y axis as shown. The rod extends to infinity in both directions. Which of the following expressions gives the magnitude of the electric field at a point P located a distance d from the rod on the x axis?
E= λ/4πε₀x
A metal sphere with a net charge Q is at the center of an insulating sphere of radius R. What is the magnitude of the electric field at a point located at r > R?
E=(1/4πε₀)(Q/r²)
Which one of the following expressions gives the correct relationship between the magnitudes of the electric and magnetic fields of an electromagnetic wave?
E=cB
Which of the following expressions gives the electric field due to an infinite sheet of charge with a uniform charge density σ?
E=σ/2ε₀
Two parallel infinite sheets of charge carry equal charge distributions σ of opposite sign. Which of the following expressions gives the electric field in the region between the infinite sheets?
E=σ/ε₀
Two objects, A with charge +Q and B with charge +4Q, are separated by a distance r. The magnitude of the force exerted on the second object by the first is F. If the first object is moved to a distance 2r from the second object, what is the magnitude of the electric force on the second object?
F/4
Which of the following laws, principles, or definitions describes the electric flux through a surface that encloses a charge?
Gauss' law
Under what circumstances is the potential difference equal to 0 V?
The electric field is perpendicular to the path at all points between initial and final points.
Why must the electric field at the surface of a conductor be perpendicular to the surface?
If it was not perpendicular, then charges on the surface would be moving.
A negatively-charged particle is slowly moving as it enters a region that has a constant magnetic field. If the velocity of the particle is initially parallel to the magnetic field, what will be the subsequent motion of the particle?
It will follow a straight line path in the same direction as it was initially traveling.
How does the resistivity of a metal wire change if either the number of electrons per unit volume increases or the mean free time increases?
In both cases, the resistivity will decrease.
What effect, if any, does increasing the capacitance in an RC circuit have on the charging of the capacitor?
Increasing the capacitance increases the charging time since the capacitor can hold more charge.
How is the direction of current flow defined in a conductor?
It is in the direction that positively-charged particles would move.
A negatively-charged particle is slowly moving as it enters a region that has a constant magnetic field. If the velocity of the particle is initially perpendicular to the magnetic field, what will be the subsequent motion of the particle?
It will follow a circular path in the plane perpendicular to the magnetic field lines.
Which of the following combination of units are those for the strength of the electric field?
N/C
Can an object carry a charge of 2.0 × 10⁻¹⁹ C?
No, because charge is quantized.
Consider the drawing in which someone is pulling a rectangular conducting loop out of a region containing a magnetic field at a constant velocity. Which one of the following is an expression of the rate of work, the power, the person is doing?
P=Fv
Which one of the following equations is not a valid expression for electric power P? Note: I is the current in a circuit as a result of a voltage V and R is the electrical resistance of the circuit.
P=I²R/V
The ends of a wire are connected to the terminals of a battery. For which of the following changes will the resulting current in the circuit have the largest value?
Replace the wire with one that has a larger radius.
The plane of a conducting loop is oriented parallel to the x-y plane. A magnetic field is directed in the −z direction. Which one of the following actions will not change the magnetic flux through the loop?
Rotate the loop about an axis that is directed
A coil of wire that forms a complete loop is moving with a constant speed v toward a very long, current carrying wire, only a portion of which is shown. What affect, if any, does the current carrying wire have on the coil of wire?
Since the magnetic field increases as the coil approaches the wire, a current is induced in the coil.
A charged particle, labeled A, is located at the midpoint between two other charged particles, labeled B and C, as shown. The sign of the charges on all three particles is the same. When particle A is released, it starts drifting toward B. What can be determined from this behavior?
The charge on C is larger than the charge on B.
A circuit contains a capacitor with a capacitance C and a resistor with a resistance R connected in series with a battery. Which one of the following mathematical expressions correctly represents the time constant for this circuit?
T=RC
How does the capacitance of two identical capacitors connected in parallel compare to that of one of the capacitors?
The 2 capacitors connected in parallel have a larger capacitance.
How does the capacitance of two identical capacitors connected in series compare to that of one of the capacitors?
The 2 capacitors connected in series have a smaller capacitance.
Point charge A is located at point A and point charge B is at point B. Points A and B are separated by a distance r. To determine the electric potential at the mid- point along a line between points A and B, which of the following mathematical approaches is correct?
The algebraic sum of the two electric potentials is determined at a distance r/2 from each of the charges, making sure to include the signs of the charges.
A small paramagnetic sphere is placed near the north pole of a strong bar magnet. Which one of the following statements concerning the subsequent behavior of the ball when it is released is the most likely?
The ball will roll away from the north pole.
What happens to a capacitor when an insulator is inserted between the two conductors of the capacitor?
The capacitance of the capacitor increases.
Capacitor B has one-half the capacitance of capacitor A. How does the charge on capacitor A compare to that on B when the two are connected in series to a battery for a long time?
The charge in capacitor A is the same as the charge on capacitor B.
Capacitor B has one-half the capacitance of capacitor A. How does the charge on capacitor A compare to that on B when the two are connected in parallel with a battery for a long time?
The charge on capacitor A is twice the charge on capacitor B.
The plates of a parallel plate capacitor are fully charged by connecting it to a battery. An insulator with a dielectric constant κ = 1.0 is then inserted between the plates. What is the effect on the charge on the plates of the insertion of the insulator?
The charge on the plates remains unchanged.
Gauss' law may be written: phi=q/ε₀. Which of the following statements concerning the charge q is true?
The charge q is the sum of all charges inside the Gaussian surface.
What effect, if any, does increasing the resistance in an RC circuit have on the charging of the capacitor?
The charging time will increase as the resistance is increased because the rate at which charges are moving to the capacitor decreases.
A conductor that is initially electrically neutral is touched by a rod that has a net positive charge. Which of the following statements describing the conductor after the rod is removed is true?
The conductor will have a net positive charge
An RC circuit contains a battery, a switch, a resistor, and a capacitor - all connected in series. Initially, the switch is open and the capacitor is uncharged. Which one of the following statements correctly describes the current in the circuit during the time the capacitor is charging?
The current is decreasing with increasing time.
A voltage V is applied to a device of resistance R; and the current through the device is I. If the device obeys Ohm's law, what will be the outcome if the voltage is increased to 2V?
The current will increase to 2I.
Which one of the following statements is a consequence of charge being conserved?
The difference between the number of positive and negative charges does not change for a given system.
The intensity of electromagnetic wave A is one fourth that of wave B. How does the magnitude of the electric field of wave A compare to that of wave B?
The electric field amplitude of wave A is one half that of wave B.
A parallel plate capacitor is fully charged at a potential V. A dielectric with constant κ = 4 is inserted between the plates of the capacitor while the potential difference between the plates remains constant. Which one of the following statements is false concerning this situation?
The electric field between the plates increases by a factor of 4.
Wires A and B are identical, except that the length of wire A is one- half that of wire B. If the same potential difference is applied between the two ends of each wire, how does the electric field within wire A compare to that in wire B?
The electric field in wire A is twice that in wire B.
Which one of the following statements best describes the concept of the electric field?
The electric field is a distribution of vectors at points due to the presence of one or more charged objects creating a scalar potential field.
Which one of the following statements concerning the electric field inside a conductor is true if electrons are moving from right to left in a conducting wire?
The electric field is directed toward the right.
A large sheet of electrically insulating material has a uniform charge density σ. Let's compare the electric field produced by the insulating sheet with that produced by a thin metal (electrically conducting) slab with σ/2 charge density distributed on one large surface of the slab and σ/2 distributed over the surface on the opposite side. How does the electric field at a distance d from each surface compare?
The electric field near the insulating sheet is the same as that near the conducting slab.
The plates of an isolated parallel plate capacitor with a capacitance C carry a charge Q. The plate separation is d. Initially, the space between the plates contains only air. Then, a Teflon (κ = 2.1) sheet of thickness 0.5d is inserted between, but not touching, the plates. How does the electric field between the plates change as a result of inserting the Teflon sheet?
The electric field will decrease to approximately one half its initial value.
Which of the following occurs when part of an electric circuit is connected to ground?
The electric potential at the connection point is equal to zero volts.
A uniform electric field is directed parallel to the +y axis. If a positive test charge begins at the origin and moves upward along the y axis, how does the electric potential vary, if at all?
The electric potential will decrease with increasing y.
Two positively charged particles are separated by a distance r. Which of the following statements concerning the electrostatic force between acting on each particle due to the presence of the other is true?
The electrostatic force depends on r².
The plates of an isolated parallel plate capacitor are separated by a distance d and carry charge of magnitude q. The distance between the plates is then reduced to d/2. How is the energy stored in the capacitor affected by this change?
The energy decreases to one half of its initial value.
A parallel plate capacitor is connected to a battery that maintains a constant potential difference across the plates. Initially, the space between the plates contains only air. Then, a Teflon (κ = 2.1) sheet is inserted between, but not touching, the plates. How does the stored energy of the capacitor change as a result of inserting the Teflon sheet?
The energy will increase.
Three capacitors are connected in series to a battery. Which one of the following statements concerning this situation is true?
The equivalent capacitance is less than the sum of the individual capacitances.
Three capacitors are connected in parallel to a battery. How is the equivalent capacitance for this circuit determined?
The equivalent capacitance is the sum of the 3 capacitances.
Which one of the following statements concerning the magnetic force on a charged particle in a magnetic field is true?
The force depends on the component of the particle's velocity that is perpendicular to the field.
A negatively-charged particle travels parallel to magnetic field lines within a region of space. Which one of the following statements concerning the force exerted on the particle is true?
The force has a magnitude of 0 N.
Consider the two charges shown in the drawing. Which of the following statements correctly describes the magnitude of the electric force acting on the two charges? q₁=+3.2µC q₂=-1.6µC
The force on q₁ has the same magnitude as that of the force on q₂.
Consider the following hypothetical situation: An infinitely long line of charge is located along the central axis of an infinitely long hollow cylinder of charge. Which of the following statements concerning the force on the line of charge is true?
The force on the line of charge is 0 N.
For an RLC circuit in the limit of very high frequency, what is the effective behavior of the capacitor and the inductor in the circuit?
The inductor acts like a very large resistance and the capacitor acts like a very small resistance.
An initially unmagnetized iron bar is placed next to a solenoid. Which one of the following statements describes the iron bar after the solenoid is connected to the battery?
The magnetic field of the solenoid induces magnetism in the bar with the bar's north pole nearest to the solenoid.
A circular loop of wire is placed in a magnetic field such that the plane of the loop is perpendicular to the magnetic field. The loop is then connected to a battery and a current then flows through the loop. Which one of the following statements concerning this situation is true?
The magnetic force exerts a net torque on the loop.
A paramagnetic powder is placed into a weak, constant magnetic field at room temperature. How does the magnetization of the powder change as its temperature is slowly increased?
The magnetization will decrease with the temperature.
Two negatively-charged objects are located on the x axis, equally distant from the origin as shown. Consider the electric field at the point P1. How will that electric field change if a third object with a charge +q is placed at point P2? Note: the point P2 is the same distance from the origin as the point P1 and the magnitude of each of the charges is the same.
The magnitude of the electric field will decrease by 25%.
Which one of the following statements concerning the measured values of the spin angular momentum is true?
The measured component of the spin angular momentum can only have one of two possible values that differ only in the sign.
An ammeter is connected to a coil of wire. A magnet is sitting motionless next to the wire such that its south end is near the coil and perpendicular to the plane of the coil as shown. The meter indicates that a current is flowing through the wire from the left toward the right. What, if anything, is wrong with this picture?
The needle should indicate that there is no current flowing.
A charged particle is located at a distance R/2 from the center of a uniformly charged hollow sphere of radius R. What is the net electrostatic force on the charged particle?
The net electrostatic force on the particle will be zero newtons because the vector sum of all of the forces on it due to the charges on the sphere is zero, so they exert no force on it.
A charged particle is located at the center of a uniformly charged hollow sphere. What is the net electrostatic force on the charged particle?
The net electrostatic force on the particle will be zero newtons because the vector sum of all of the forces on it due to the charges on the sphere is zero, so they exert no force on it.
When the distance between charged parallel plates of a capacitor is d, the capacitance is C. If the distance is increased to 2d, how will the capacitance change, if at all?
The new capacitance would be one half of the previous value.
When the distance between charged parallel plates of a capacitor is d, the potential difference is V. If the distance is decreased to d/2, how will the potential difference change, if at all?
The new potential difference would be one half of the previous value.
A positively-charged object is released from rest in a region containing a uniform electric field. Which one of the following statements concerning the subsequent motion of the object is correct?
The object will experience a constant acceleration and move in the direction of the electric field.
Which one of the following conditions is not a requirement for a particle to experience a magnetic force when placed in a magnetic field?
The particle must not be under the influence of any other forces.
A positively-charged particle is stationary in a constant magnetic field within a region of space. Which one of the following statements concerning the particle is true?
The particle will not move.
Wires A and B are identical except that each is made from a different material. The one end of wire A is connected to one end of wire B. The two remaining ends are connected across a battery and current flows through the two wires. Which one of the following statements concerning this situation is true?
The potential difference across the 2 wires is different, but the current through each wire is the same.
Capacitor B has one-half the capacitance of capacitor A. How does the potential difference on capacitor A compare to that on B when the two are connected in series with a battery for a long time?
The potential difference on capacitor A is one-half the charge on capacitor B.
Two positively charged particles are separated by a distance r. The force on particle 1 is F due to particle 2. The force on particle 2 is 2F due to particle 1. Is the previous sentence true or false? Explain why this is the case.
The sentence is false because the forces on each of the two objects are equal in magnitude, but opposite in direction.
When you calculate the potential at some point P due to a continuous charge distribution, the sign for the potential can be troublesome. If the charge distribution is negative, should the quantities dq and λ represent negative quantities?
The signs can be ignored; and at the end of the calculation inserted. The potential is negative if the charge distribution is negative.
A battery charges capacitor A until the potential difference between the two conductors of the capacitor is V. A second, identical capacitor, labeled B, is charged by another battery until the potential difference of capacitor B is 2V. How does the stored energy of capacitor B compare to that of capacitor A?
The stored energy of capacitor B is 4x that of capacitor A.
While analyzing the currents within a circuit containing multiple components (such as batteries, resistors, etc.), which of the following statements concerning currents flowing into a single junction must be true?
The sum of the currents entering the junction must equal the sum of the currents exiting the junction.
In July, Joe set up his fixed array of solar panels to maximize the amount of electricity output from the array when the Sun was high in the sky. Unfortunately, Joe finds that the array doesn't operate as well during the winter months, even though there is nothing physical wrong with the array. What is the most likely cause of Joe's winter problem?
The sun is lower in the sky during the winter, so sunlight strikes the solar panels at an angle.
Two positively charged particles are in fixed locations on the x axis. A test charge that is free to move about the x-y plane is placed at the mid-point between the two positively charged particles. If the test charge is held stationary at the mid-point and then released, it remains stationary. Which of the following is the best explanation for this behavior?
The test charge is at a point of stable equilibrium for the x direction, but not for the y direction.
When a battery, a resistor, a switch, and an inductor form a circuit and the switch is closed, the inductor acts to oppose the change in the current. How is the time constant of the inductor affected by doubling the resistance in the circuit?
The time constant would decrease to one-half its original value.
Why does the electric field due to a dipole decrease more rapidly with increasing distance than that for a single charge?
The total charge of the dipole is neutral (zero).
Consider the two charged particles. One charge located on the y axis has a value −2q and is located at a distance r from the origin, point O. The other charge has a value −q and is located at a distance 2r from the origin along the x axis. Which one of the following statements concerning the electric potential at the origin is true?
The total electric potential at the origin is equal to -5kq/2r.
Two electrons are separated by a distance R. If the distance between the charges is increased to 2R, what happens to the total electric potential energy of the system?
The total electric potential energy of this system would decrease to one half its initial value.
A uniform electric field is directed in the negative x direction. If you were to move a positive charge in the positive x direction, how would the total energy of the positive charge / electric field system change, if at all?
The total energy of the system would increase.
A portion of a loop of wire passes between the poles of a magnet as shown. We are viewing the circuit from above. When the switch is closed and a current passes through the circuit, what is the movement, if any, of the wire between the poles of the magnet?
The wire moves downward (away from us).
Consider a circuit that contains an ideal battery and a resistor to form a complete circuit. Which one of the following statements concerning the work done by the battery is true?
The work done is equal to the thermal energy dissipated by the resistor.
A force is exerted on a positively-charged particle that moves the particle in the direction opposite to that of an electric field. Which one of the following statements concerning the work performed in this movement is true?
The work done on the particle has a negative sign.
A positive charge is located at the origin. What is the direction of the electric potential of the positive charge?
There is no direction since the electric potential is a scalar quantity.
Four charges are located on the corners of a square as shown in the drawing. What is the direction of the net electric field at the point labeled P? +q -q -q +q
There is no direction. The electric field at P is 0 N/C.
Gauss' law can be used to prove that all excess charge in a conductor distributes itself on the surface of the conductor. Which one of the following choices is a consequence of this proof?
There would be a non-zero electric field if any net charge was not on the surface.
A laser beam is directed at the left side of a plastic block (n = 1.53) as shown at an angle θ. The beam then undergoes total internal reflection as the light strikes the top interface at the critical angle for the block and the surrounding air. What is the value of the angle θ?
This is not possible since no angle θ will satisfy this situation.
Which of the following choices represents the quantity that is equal to the electric potential?
U/q
A positively-charged particle is held at point A between two parallel metal plates. The plate on the left has a net positive charge +q and the plate on the right has a net negative charge −q. The particle is then moved to point B. How does the electric potential energy at point A compare with that at point B?
Ua>Ub
Which one of the following choices is not a possible way to produce a magnetic field?
Uniformly distribute charges over the surface of a conductor.
Which of the following will occur when a diamagnetic material is placed in an external magnetic field?
Weak magnetic dipole moments will be induced that are generally aligned in opposition to the applied field.
Two resistors can be either connected to a battery in series or in parallel. In which case, if either, is the equivalent resistance the smallest?
When the two resistors are wired in parallel, the equivalent resistance is less than if they are wired in series.
Complete the following statement: Lenz's law indicates that induced currents form to oppose
a change in the magnetic flux
A circuit contains a battery, a switch, an inductor, and a resistor connected in series. Initially, the switch is open. In which one of the following intervals does the energy stored in the inductor have the largest value?
a long time after the switch is closed
In which one of the following cases will total internal reflection occur? a) Light is traveling in a material that has a smaller index of refraction than material surrounding it. b) Light is traveling in a material that has a larger index of refraction than material surrounding it. c) Light is traveling from a material that has a larger index of refraction into a material that has a smaller index of refraction. d) Light is traveling through a material with a high degree of chromatic dispersion.
a) Light is traveling in a material that has a smaller index of refraction than material surrounding it.
Which one of the following statements concerning electrical conductors is false? a) Rubber is an excellent electrical conductor. b) A material that is a good electrical conductor has many free electrons that can easily move around inside the material. c) When a positively-charged object is moved into contact with an electrical conductor, electrons move toward the object. d) Materials that are good thermal conductors are often good electrical conductors. e) Most metals are very good electrical conductors.
a) Rubber is an excellent electrical conductor.
Which one of the following statements concerning the conventional direction of current is true? a) The conventional direction of current is the hypothetical direction of movement of positive charges through the wires of an electric circuit. b) The conventional direction of current is the direction of movement of electrons through the wires of an electric circuit. c) The conventional direction of current is equal to the electromotive force of the battery in an electric circuit. d) The conventional direction of current is always a clockwise movement around a circuit. e) The conventional current is the one that moves in a dc circuit and an unconventional current is one that moves in an ac circuit.
a) The conventional direction of current is the hypothetical direction of movement of positive charges through the wires of an electric circuit.
Which one of the following statements concerning the electric dipole moment is false? a) The dipole moment is a scalar quantity. b) The dipole moment has units of C⋅m. c) The dipole moment combines two intrinsic properties of an electric dipole, the distance between the charges and the amount of charge on each object. d) The dipole moment is directed from the negative charge toward the positive charge of the dipole. e) The direction of the dipole moment is used to specify the orientation of the dipole.
a) The dipole moment is a scalar quantity.
Which one of the following statements is true concerning resistors connected in parallel within an electric circuit? a) The potential difference across each of the resistors is the same. b) The current through each of the resistors is the same. c) The energy dissipated by each of the resistors is the same. d) The resistance of each of the resistors is the same. e) The resistivity of each of the resistors is the same.
a) The potential difference across each of the resistors is the same.
Which one of the following statements concerning the electric field is false? a) The SI unit of the electric field is the newton per meter (N/m) b) The electric field is a vector quantity. c) At a given point, a charged particle will experience a force, if an electric field is present at that location. d) If a positively-charged particle is placed at a location where the electric field is directed due north, it will be accelerated due north. e) The magnitude of the electric field at a particular location due to a particular charged particle is inversely proportional to the distance of the particle from that location.
a) the SI unit of the electric field is the newton per meter (N/m)
Which of the following devices is placed into a circuit to measure the current that passes through it?
ammeter
A sphere has a radius R and a total charge Q uniformly distributed throughout its volume. Where is the electric potential of the sphere a minimum?
at infinity
Which one of the following statements concerning the electric force is true? a) Two charged objects with identical charges will exert an attractive force on one another. b) It is possible for a small negatively-charged particle to float above a negatively charged surface. c) A positively-charged object is attracted toward another positively- charged object. d) The electric force cannot alter the motion of an object. e) Newton's third law of motion does not apply to the electrostatic force.
b) It is possible for a small negatively-charged particle to float above a negatively charged surface.
Which one of the following statements is true concerning resistors connected in series within an electric circuit? a) The potential difference across each of the resistors is the same. b) The current through each of the resistors is the same. c) The energy dissipated by each of the resistors is the same. d) The resistance of each of the resistors is the same. e) The resistivity of each of the resistors is the same.
b) The current through each of the resistors is the same.
Which of the following phrases best describes the term "magnetic flux"? a) the direction of the magnetic field relative to a surface b) the amount of magnetic field that passes through a surface c) the number of magnetic dipoles moving through a wire d) the flow of magnetons in space e) Choice (a) and (b) are both correct.
b) the amount of magnetic field that passes through a surface
Electric potential energy is defined in a similar manner to the gravitational potential energy. Complete the following statement: These two potential energies are analogous to each other because
both the electric and gravitational forces are conservative forces
When an electron (charge −1.60 × 10−19 C) and a positron (charge +1.60 × 10−19 C) come together, they annihilate one another. Two particles of light (photons) are emitted from the annihilation. This is an example of what type of physical phenomena?
charge conservation
By which of the following methods could the current in a given circuit be doubled? a) Either double the resistance or double the voltage. b) Reduce either the voltage or the resistance to half of the initial value. c) Either double the voltage or reduce the resistance to half of its initial value. d) Either double the resistance or reduce the voltage to half of its initial value. e) None of the above answers are correct.
c) Either double the voltage or reduce the resistance to half of its initial value.
For which combination for the length L and radius r of a wire will the resistance have the smallest value? a) L = 0.50 m and r = 0.03 m b) L = 0.25 m and r = 0.08 m c) L = 0.40 m and r = 0.2 m d) L = 0.80 m and r = 0.1 m e) L = 0.10 m and r = 0.05 m
c) L = 0.40 m and r = 0.2 m
Which of the following statements concerning the electric field inside a conductor is true? a) The electric field inside a conductor is never zero N/C. b) The electric field inside a conductor is always zero N/C. c) The electric field inside a conductor can only be non-zero if charges inside the conductor are moving. d) The electric field inside a conductor is always zero N/C, unless there are excess charges inside the conductor. e) Two or more of the above answers are correct.
c) The electric field inside a conductor can only be non-zero if charges inside the conductor are moving.
A circuit contains a battery and a resistor of resistance R. For which one of the following combinations of current and voltage does R have the smallest value? a) V = 9 V and I = 0.002 A b) V = 12 V and I = 0.5 A c) V = 1.5 V and I = 0.075 A d) V = 6 V and I = 0.1 A e) V = 4.5 V and I = 0.009 A
c) V = 1.5 V and I = 0.075 A
An alternating current is set up in an LRC circuit. For which of the following circuit elements does the current lead the voltage by 90°?
capacitor only
Consider the situation shown. A triangular, aluminum loop is slowly moving to the right. Eventually, it will enter and pass through the uniform magnetic field region represented by the tails of arrows directed away from you. Initially, there is no current in the loop. When the loop is exiting the magnetic field, what will be the direction of any induced current present in the loop?
clockwise
The fact that the sum of the currents entering any junction in an electric circuit must be equal to the sum of the currents leaving the junction is an expression of what principle?
conservation of charge
Lenz's law is a consequence of what other physical law?
conservation of energy
What is the name for the principle or law that allows one to determine the average intensity of polarized light that will be transmitted through a sheet of polarizing material?
cos² rule
A copper wire is fabricated that has a gradually increasing diameter along its length as shown. If an electric current is moving through the wire, which quantities vary along the length of the wire?
current density and electric field only
Which one of the following statements concerning electromagnetic waves is false? a) One form of electromagnetic radiation is visible light. b) All electromagnetic waves travel through a vacuum region at the speed of light. c) All electromagnetic waves are transverse waves. d) All electromagnetic waves have the same frequency. e) Electromagnetic waves can travel through solids, liquids, gases, and vacuum regions.
d) All electromagnetic waves have the same frequency.
Which one of the following statements concerning charge distributions is false? a) Charge distributions consist of a very large number of closely spaced charges. b) Charge distributions may be uniform arrangements of charges along a line, over a surface, or throughout a volume. c) Calculus provides important tools for determining electric fields due to charge distributions. d) Charge distributions are treated as though composed of discrete charges. e) In dealing with charge distributions, it is often more useful to speak in terms of a charge density rather than the total charge.
d) Charge distributions are treated as though composed of discrete charges.
Which one of the following choices is not one of Kirchoff's rules? a) junction rule b) emf rule c) loop rule d) slide rule e) resistance rule
d) slide rule
Which of the following terms is used to describe materials that have weak induced magnetic dipole moments that are directed in the opposite direction to an applied external magnetic field?
diamagnetic
To make silicon useful for electronic circuits, impurity atoms must be added. What is the name of this process?
doping
What is the term used to describe the net motion of electrons when an electric field is applied to a conductor and a current is established?
drift speed/velocity
An electron traveling due east in a region that contains only a magnetic field experiences a vertically downward force, toward the surface of the earth. What is the direction of the magnetic field?
due north
Which of the following choices best gives the benefit(s) of using AC over using DC? a) The length of wires is less relevant. b) Power may be transferred over long distances using higher voltage and low current. c) The potential difference may be varied using transformers. d) Any potential loss in resistive elements is negligible. e) All of the above answers are benefits of AC over DC.
e) All of the above answers are benefits of AC over DC.
Which of the following statements concerning electric field lines is false? a) Electric field lines between two charged particles are often curved. b) Electric field lines are a method proposed by Michael Faraday to map the electric field at various locations. c) Electric field lines can be used to indicate the local magnitude of the electric field. d) Electric field lines are always directed radially away from a positively- charged particle. e) An electric field line indicates the direction of the force on an electron placed on the line.
e) An electric field line indicates the direction of the force on an electron placed on the line.
What does the Poynting vector at a given point describe? a) the direction of the electric field b) the direction of the magnetic field c) the direction the wave is traveling d) the direction in which energy is transported e) Both (c) and (d) are correct.
e) Both (c) and (d) are correct.
Coulomb's law is similar to Newton's law of gravitation in several ways. Which one of the statements is not a similarity between these two laws? a) In both laws, the force is inversely proportional to the square of the distance between two particles. b) In both laws, the force decreases with increasing distance between the two particles. c) In both laws, the force is proportional to the product of an intrinsic property of each of the two particles. d) In both laws, there is a proportionality constant that appears. e) In both laws, the force is always one of attraction between the two particles.
e) In both laws, the force is always one of attraction between the two particles.
Which one of the following sentences best describes the term refraction? a) Light is reflected at the interface between two transparent media. b) The angle of incidence does not equal the angle of reflection at the interface between two materials. c) Light is divided along two paths at an interface between two materials. d) The direction of light is along a straight line as it passes from one material into another, regardless of the angle of incidence. e) Light travels through the boundary of two different materials.
e) Light travels through the boundary of two different materials.
Which one of the following materials is not ferromagnetic? a) cobalt b) nickel c) gadolinium d) iron e) aluminum
e) aluminum
Which of the following does not significantly contribute to the magnetism of a given material? a) the spin magnetic moment of protons b) the spin magnetic moment of neutrons c) the spin magnetic moment of electrons d) the angular magnetic moment of electrons e) both (a) and (b)
e) both (a) and (b)
Which of the following types of waves is not part of the electromagnetic spectrum? a) microwaves b) gamma rays c) ultraviolet radiation d) radio waves e) sound waves
e) sound waves
You are looking down on a long, straight cable that is carrying current toward the north. What is the direction of the magnetic field due to the current at your location?
east
When a metal sheet is pulled from a region containing a magnetic field, currents are induced in the metal sheet. What is the name given to these currents?
eddy currents
Which of the following is most responsible for the magnetic behavior of materials?
electrons
Complete the following statement: The sum of the magnitudes of the currents directed into a junction
equals the sum of the magnitudes of the currents directed out of the junction.
What is the name given to the quantum mechanical effect that gives rise to ferromagnetism in materials, such as iron, cobalt, and nickel?
exchange coupling
What is the SI unit for capacitance?
farad (F)
Which of the following terms is used to describe materials that have regions in which strong magnetic dipole moments are aligned with each other?
ferromagnetic
Complete the following sentence: an electric insulator has...
few electrons available to conduct electricity
The insulated wiring in a house can safely carry a maximum current of 18 A. The electrical outlets in the house provide an alternating voltage of 120 V. A space heater when plugged into the outlet operates at an average power of 1500 W. How many space heaters can safely be plugged into a single electrical outlet and turned on for an extended period of time?
one
The direction of the electric field is the same as which of the following properties related to a test charge?
force on a positive test charge
A charged particle is moving in a magnetic field. What is the direction of the force on the particle due to the magnetic field?
in the direction that is perpendicular to both the magnetic field and the velocity
In the fabrication of an electrical extension cord, the manufacturer wants to reduce the overall resistance of the wires in the extension cord. Which of the following changes would result in the lowest resistance?
increase the diameter of the wires
Which term is used to describe a material that does not allow electrons to easily move through it?
insulator
Which one of the following types of materials exhibits the largest values of resistivity?
insulators
Which one of the following terms describes the resistance that a battery (or other emf device) has in a circuit?
internal resistance
Which one of the following rules, laws, or principles describes how the net electric charge of an isolated system undergoing any process remains constant?
law of conservation of electric charge
Complete the following sentence: the electrical resistivity of most metal wires is
much smaller than the values for most semiconductors
Which one of the following terms is used for the effect in which a changing current in one circuit induces an emf in another circuit?
mutual induction
Gauss' law relates the electric field to ______ at points on a Gaussian surface.
net charge enclosed by the surface
When you calculate the electric flux through a Gaussian surface, of what are you determining the flow through the surface?
not charge, electric current, electric energy or electric field
As shown in the drawing, a positively charged particle remains stationary between particles A and B. The positively charged particle is one- quarter the distance between the two other particles, as shown. What can be concluded from the situation?
nothing
Which one of the following changes will necessarily increase the capacitance of a capacitor?
placing a dielectric between the plates
An initially electrically neutral conducting sphere is placed on an insulating stand. A negatively-charged glass rod is brought near, but does not touch the sphere. Without moving the rod, a wire is then attached to the sphere that connects it to earth ground. The rod and wire are then removed simultaneously. What is the final charge on the sphere?
positive
A conducting sphere is connected via a wire to the ground. For a very short time, electrons move from the ground to the sphere. Then, no more electrons move to the sphere. Complete the following sentence: Before the wire was connected, the sphere's electric potential had a
positive value
The magnitude of the electric field within a conducting wire depends on which of the following quantities?
potential difference, wire length, and wire conductivity only
Which pair of terms correctly fills the blanks in the following sentence? ________ is a property of an object while ________ is a property of a material.
resistance, resistivity
An alternating current is set up in an LRC circuit. For which of the following circuit elements are the current and voltage in phase?
resistor only
Silicon is an example of what type of material?
semiconductor
Which one of the following expressions is Brewster's law?
tanθB=n₂/n₁
What is capacitance?
the amount of charge needed to produce a certain potential difference across a capacitor
For a cylindrical capacitor, the capacitance does not depend on which of the following values?
the amount of charge on the conductors
Complete the following statement: Current density is a measure of
the amount of current flowing through a cross-sectional area
Complete the following statement: The polarization direction of an electromagnetic wave is determined by
the direction of the electric field component
Electric field lines depend on...
the direction of the field, the strength of the field, the force exerted on a test charge
Complete the following statement: When a dielectric with constant κ is inserted between the plates of a charged isolated capacitor
the electric field between the plates is reduced by a factor of κ
Complete the following statement: Along an equipotential surface,
the electric field lines are perpendicular to the surface.
A circuit contains an inductor, a capacitor, and a light bulb connected as shown. In which frequency limit is the light bulb the brightest?
the high frequency limit
What produces the magnetism of an individual atom?
the orbital and spin motions of electrons
Which one of the following phrases best describes the electric potential of a charged particle?
the potential energy per unit charge
Which one of the following is a primary consideration in determining the capacitance of a parallel-plate capacitor?
the size and separation of the plates
Which one of the following quantities remains constant for a given LC circuit?
the sum of the energy stored in the capacitor and that in the inductor
A single, positive test charge is brought near a dipole. Under what circumstances will the force exerted on the test charge by the dipole be given by F=de²/2πε₀z³?
the test charge is very far from the dipole compared to the distance between the dipole charges
The drawing shows a hollow conducting sphere with a net positive charge uniformly distributed over its surface. A small negatively- charged object has been brought near the sphere as shown. What is the direction of the electric field at the center of the sphere?
to the right
An electron, which has a charge of 1.60 × 10−19 C, is released at rest in a uniform electric field of magnitude 120 N/C. What is the potential energy of the electron just before it is released from rest?
too little information is given to determine an answer
Four charges are located on the corners of a square as shown in the drawing. What is the direction of the net electric field at the point labeled P? +2q -q -2q +q
toward the middle of the bottom side of the square
A spherical Gaussian surface of radius R is surrounding a particle with a net charge q. If the spherical Gaussian surface is replaced by a cube, under what conditions would the electric flux through the sides of the cube be the same as through the spherical surface?
under all conditions
An electron traveling horizontally to the right enters a region where a uniform electric field is directed downward. What is the direction of the force exerted on the electron once it has entered the field?
upward
When lightning strikes, the current flows from the ground upward to the clouds above. What is the direction of the electric field of the lightning?
upward
A long wire carries a current toward the east in a magnetic field that is directed due south. What is the direction of the magnetic force on the wire?
vertically downward
Which of the following units are the SI units for the electric potential?
volt (V)
Which one of the following units is the correct SI unit for the electromotive force (emf)?
volts (V)
A long wire carries a current toward the north in a magnetic field that is directed vertically downward. What is the direction of the magnetic force on the wire?
west
In most cases, Ohm's law is valid when which of the following conditions is satisfied?
when, for a given piece of material, the ratio V/I is the same for a wide range of voltages and currents
A conducting bar slides with a velocity v to the right on some conducting rails as shown. A uniform magnetic field is directed perpendicular to the bar. Answer the following two questions: (1) Will the light bulb "turn on" in this case? and (2) How is the magnetic flux through the conducting loop changing, if at all, as the bar slides to the right?
yes, the magnetic flux increases
Unpolarized light of intensity S is directed toward three polarizing sheets. The first sheet is polarized vertically; and the last sheet is oriented horizontally. If the middle sheet is also oriented vertically, what is the intensity of the light exiting the last polarizer?
zero
A conducting sphere (shown in grey in the drawing) of radius R has a charge q distributed uniformly over its surface. A spherically-shaped Gaussian surface with a radius r < R is represented in the drawing by the dashed circle. Applying Gauss' law, what is the magnitude of the electric field inside the Gaussian sphere?
zero N/C
A spherical conductor has a radius R and a tiny spherical cavity at its center that has a radius R/10. The conductor is otherwise solid. Inside the cavity is a positive charge Q. What is the electric field at a distance R/2 from the center?
zero N/C
The drawing shows two long, straight wires that are parallel to each other and carry a current of magnitude i toward you. The wires are separated by a distance d; and the centers of the wires are a distance d from the y axis. Which one of the following expressions correctly gives the magnitude of the total magnetic field at the origin of the x, y coordinate system?
zero Tesla
Which one of the following is the correct expression for the angular frequency of oscillation for an LC circuit?
ω=1/√LC
A coil of wire with N turns and area A is placed into a magnetic field of magnitude B. The angle of the normal to the plane of the coil is at an angle θ with respect to the magnetic field. According the Faraday's law, which of the following changes will produce an emf in a coil of wire?
∆B, ∆A, and/or ∆θ
