All of the Clicker Question For Exam #2
Complete the following statement by filling in the blank: An electric generator generates electrical energy from ________________________, just the opposite of what a motor does. mechanical work electric potential energy thermal energy gravitational potential energy electromagnetic energy
mechanical work
What is the origin of motional emf? changing magnetic field strength changing direction of the magnetic field moving atomic nuclei through an electric field moving electrons through a magnetic field changing temperature conditions of a conductor
moving electrons through a magnetic field
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? Lenz effect coherence interference self-induction mutual induction
mutual induction
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? seventy-five percent twenty-five percent ten percent one hundred percent fifty percent
one hundred percent
What is the use of a bubble chamber? to make a magnetic field within a region of space uniform to allow the trajectory of charged particles moving in a magnetic field to be observed and measured to increase the mass of charged particles so that their trajectories are more easily observed to charge a neutral particle or the increase the charge on a particle before it enters a magnetic field to accelerate charged particles before they move into a magnetic field
to allow the trajectory of charged particles moving in a magnetic field to be observed and measured
A long wire, parallel to the ground, 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? west east vertically upward vertically downward north
vertically downward
What are the units of light intensity? watts/meter2 (W/m2) tesla/meter3 (T/m3) joules/meter3 (J/m3) newtons/coulomb (N/C) joules/meter2 (J/m2)
watts/meter2 (W/m2)
Complete the following statement: Faraday's law indicates that a changing magnetic field produces light. global warming. an induced magnetic field. a force field. an electric field.
an electric field.
A magnetic field is directed due north. A vertical metal bar moving due east enters the magnetic field. Which one of the following phenomena is likely to occur? The bar will become ferromagnetic. The bar will reduce the strength of the magnetic field on all sides of the bar. The bar will be accelerated by the magnetic field. The bar will melt under the influence of the magnetic field. A motional emf will appear between the ends of the bar.
A motional emf will appear between the ends of the bar.
Which one of the following statements concerning electromagnetic waves is false? All electromagnetic waves have the same frequency. Electromagnetic waves can travel through solids, liquids, gases, and vacuum regions. One form of electromagnetic radiation is visible light. All electromagnetic waves are transverse waves. All electromagnetic waves travel through a vacuum region at the speed of light.
All electromagnetic waves have the same frequency.
The drawing shows four situations A, B, C, and D in which an observer and a source of electromagnetic waves are moving along the same line. In each case the source emits a wave of the same frequency, and in each case only the source or the observer is moving. The arrow in each situation denotes the velocity vector, which has the same magnitude in each situation. When there is no arrow, the observer or the source is stationary. Rank the frequencies of the observed electromagnetic waves in descending order (largest first) according to magnitude. C and D (a tie), A and B (a tie) A and B (a tie), C and D (a tie) A and D (a tie), B and C (a tie) B and D (a tie), A and C (a tie) B and C (a tie), A and D (a tie)
B and D (a tie), A and C (a tie)
Which one of the following choices correctly indicates the proportionality between magnetic field due to a current carrying, long straight wire and the distance R from the wire?
B is proportional to 1/R.
. A circular ring is rotated clockwise at a constant rate for an extended period of time using the apparatus shown. Which of the graphs below correctly shows the magnetic flux through the ring as a function of time? Note: At time t = 0 s, the plane of the ring is perpendicular to the direction of the magnetic field.
C
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 helical path around the magnetic field lines. It will follow a circular path in the plane perpendicular to the magnetic field lines. It will follow a circular path in a plane parallel to the magnetic field lines. It will follow a parabolic path as the speed increases. It will follow a straight line path in the same direction as it was initially traveling.
It will follow a circular path in the plane perpendicular to the magnetic field lines.
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 helical path around the magnetic field lines. It will follow a circular path in a plane parallel to the magnetic field lines. It will speed up along the same line of motion. It will follow a circular path in the plane perpendicular to the magnetic field lines. It will follow a straight line path in the same direction as it was initially traveling.
It will follow a straight line path in the same direction as it was initially traveling.
Which one of the following choices is not an essential part of an electric motor? magnets Josephson junction wire coil a battery or other source of emf split-ring commutator
Josephson junction
Which one of the following principle's or laws allows one to determine the direction of an induced current in a conducting loop of wire due to a changing magnetic flux? Faraday's law principle of induced magnetic flux equivalence principle Lenz's law Gauss' law
Lenz's law
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? Malus' law law of polarization Morley principle Lenz's law Feynmann's principle
Malus' law
Which of the following types of electromagnetic radiation is produced by the decay of atomic nuclei? microwaves x-rays infrared radiation gamma rays visible light
gamma rays
In the discussion of the Doppler effect for electromagnetic waves, this effect differs from that of sound waves in which of the following ways? The Doppler effect is not present when the light is passing through a vacuum. The Doppler effect for electromagnetic waves is dependent on the relative speed of the source and observer. The Doppler effect for electromagnetic waves requires that both the observer and the source be moving with respect to a medium. The Doppler effect for electromagnetic waves requires that the speed of light be measured with respect to a stationary reference frame. The frequency of the electromagnetic waves is unaffected by the relative motion of an observer and a source.
The Doppler effect for electromagnetic waves is dependent on the relative speed of the source and observer.
A magnetic field is generated by a current-carrying wire. Which one of the following statements concerning this situation is false? The direction of the magnetic field is parallel to the direction of the current in the wire. The magnitude of this magnetic field decreases with increasing distance away from the wire. The magnitude of the magnetic field is directly proportional to the magnitude of the current. Right-hand Rule No. 2 is useful for determining the direction of the magnetic field at a particular location.
The direction of the magnetic field is parallel to the direction of the current in the wire.
One type of antenna can be made that is composed of two straight wires connected to an ac generator. Which one of the following statements concerning this type of antenna and electromagnetic waves is false? The generator continually injects electrons into the wires. When one of the wires has a net positive charge, the other wire has a net negative charge. As the potential difference at the terminals varies sinusoidally, electrons move between the ends of the wires. The electric field and magnetic field vectors of the electromagnetic waves generated are perpendicular to each other when they are far from the antenna. At each position far from the antenna, the amplitude of the electric and magnetic fields is the same.
The generator continually injects electrons into the wires.
In a well-designed transformer with an iron core, the secondary coil has twice as many turns as the primary coil. Which one of the following statements concerning this transformer is true? This kind of transformer is typically used between a power transmission line and a residence. The induced emf generated in the secondary coil is twice as large as that generated in the primary coil. This is a step down transformer because the current in the secondary coil is less than that in the primary coil. The effect of the iron core is to reduce the magnetic field passing through the coils. The flux that passes through each turn of the primary coil is twice the flux that passes through each turn of the secondary coil.
The induced emf generated in the secondary coil is twice as large as that generated in the primary coil.
The drawing shows two sheets of polarizing material, each of which has its transmission axis aligned vertically. Light is incident from the left, as shown, and can be either completely unpolarized or completely polarized along the vertical direction. In either case, the average intensity of the incident light is the same, and light exits the polarizer on the right. Which one of the following statements is true concerning the intensity of the exiting light? The intensity of the exiting light is greater when the incident light is completely unpolarized. The intensity of the exiting light is greater when the incident light is completely polarized. The intensity of the exiting light is the same for both types of incident light.
The intensity of the exiting light is greater when the incident light is completely polarized.
Two long wires are parallel to each other. One wire carries a current directed due east and the other carries a current of the same magnitude, but directed due west. Which one of the following statements concerning this situation is false? The magnetic field produced by each wire has its greatest magnitude outside, but near the surface of the wire. The magnetic forces due to the currents carried by the wires causes the wires to move apart. The magnetic field in the plane of the wires at the midpoint between the two wires is equal to zero tesla. If you are looking toward the west along the wire carrying the current toward the west, the magnetic field lines are directed clockwise around the wire.
The magnetic field in the plane of the wires at the midpoint between the two wires is equal to zero tesla.
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? There is nothing wrong with the picture. The current should be flowing from the right toward the left. The needle should indicate that there is no current flowing. The needle should be slanted toward the right.
The needle should indicate that there is no current flowing.
Which one of the following statements concerning permanent magnets is false? The magnetic field is directed away from a north pole and into a south pole. Magnets can exert forces on each other. The north pole of a compass points toward the north pole of a permanent magnet. There is a magnetic field surrounding a magnet. A north pole attracts a south pole.
The north pole of a compass points toward the north pole of a permanent magnet.
An electron is traveling due south when it enters a uniform magnetic field directed due west. Which of the following statements concerning this situation is false? The subsequent motion of the electron will be the same as if there were an electric field directed due west and no magnetic field present. The direction of the magnetic field and the direction of the magnetic force on the electron are perpendicular to one another. The magnitude of the magnetic force will be constant with time. The electron will follow a curved path. The direction of the magnetic force on the electron will vary with time.
The subsequent motion of the electron will be the same as if there were an electric field directed due west and no magnetic field present.
The drawing shows two sheets of polarizing material. Polarizer 1 has its transmission axis aligned vertically, and polarizer 2 has its transmission axis aligned at an angle of 45° with respect to the vertical. Light that is completely polarized along the vertical direction is incident either from the far left or from the far right. In either case, the average intensity of the incident light is the same. Which one of the following statements is true concerning the average intensity of the light that is transmitted by the pair of sheets?
When the light is incident from the left, the transmitted intensity is one-half the incident intensity; when the light is incident from the right, the transmitted intensity is one-fourth the incident intensity.
Complete the following statement: Lenz's law indicates that induced currents form to oppose a change in the magnetic field direction. a change in the electric flux. a change in the magnetic field. the magnetic flux. a change in the magnetic flux.
a change in the magnetic flux.
Complete the following statement: The speed of light in a vacuum is larger for higher frequency electromagnetic waves. smaller for higher energy electromagnetic waves. a constant value everywhere in the universe. larger for short wavelength electromagnetic waves. larger for higher energy electromagnetic waves.
a constant value everywhere in the universe.
What is a solenoid? a radio antenna a magnet that is inserted into a coil of wire a scanning mechanism inside of a television a single loop of wire in the shape of a circle a long coil of wire in the shape of a helix
a long coil of wire in the shape of a helix
Approximately how long does it take for a radio wave to travel from the earth to the moon? a second a minute eight minutes a millisecond twenty minutes
a second
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? a) 0.17 b) 6 c) 100 d) This cannot be determined without knowing how many turns one of the coils in the transformer has.
a) 0.17
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. a) 1 b) 2 c) 3 d) 4 e) 5
a) 1
For the mass spectrometer described in the text, the magnetic field is varied to allow ions of varying mass to reach the detector. A different method would be to maintain a constant magnetic field and vary the accelerating potential difference V. Assuming the magnetic field is held at B = 0.250 T and that r = 0.0750 m, in which of the following ranges of voltages could one detect both oxygen molecules (m = 2.656 ´ 10-26 kg) and nitrogen molecules (m = 2.325 ´ 10-26 kg). a) 4200 to 4900 V b) 3300 to 4500 V c) 5100 to 6000 V d) 2100 to 3100 V e) 4800 to 5700 V
a) 4200 to 4900 V
Which one of the graphs correctly shows the relationship between capacitive reactance and frequency? a) A b) B c) C d) D e) E
a) A
What type of current results from an electric generator which is essentially a rotating planar coil of wire in a magnetic field? constant emf direct current constant current alternating current
alternating current
Three very long, parallel wires (a small portion of each is shown in the drawing) are resting on a flat surface. The distance between wire B, which has a 15 mA current to the left, and its neighbors is 0.0015 m. Wire A carries a 10 mA current toward the right; and wire C carries a 5 mA current toward the right. Each wire exerts a magnetic force on both its neighbors. Rank the wires in order of the magnitude of the net magnetic force on each, with the largest value first and the lowest value last. a) A > B > C b) B > A > C c) C > B > A d) A > C > B e) B > C > A
a) A > B > C
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? a) During the time the magnetic field is decreasing, a current is induced that is directed counterclockwise around the loop. b) During the time the magnetic field is decreasing, a current is induced that is directed clockwise around the loop. c) No current is induced in the loop at any time. d) A current is induced that is directed clockwise around the loop, which also continues after the magnetic field attains a constant value. e) A current is induced that is directed counterclockwise around the loop, which also continues after the magnetic field attains a constant value.
a) During the time the magnetic field is decreasing, a current is induced that is directed counterclockwise around the loop.
What must the initial state of motion of a charged particle be if it will follow a helical path in a magnetic field? a) It must be moving at an angle that is neither parallel to nor perpendicular to the magnetic field. b) It must be moving parallel to the magnetic field. c) It must be moving perpendicular to the magnetic field. d) It must be moving in the direction opposite to the magnetic field. e)It must be initially at rest when it is placed in the magnetic field
a) It must be moving at an angle that is neither parallel to nor perpendicular to the magnetic field.
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 or wire? a) Since the magnetic field increases as the coil approaches the wire, a current is induced in the coil. b) The rectangle will be distorted as it is pulled in the direction of the current in the wire. c) Close to the wire, a magnetic force acts on the loop that accelerates the loop away from the wire. d) Since the magnetic field around the wire is not changing, there is no effect on the coil. e) Since the coil and the wire are not touching, there is no effect.
a) Since the magnetic field increases as the coil approaches the wire, a current is induced in the coil.
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? a) The particle will not begin to move. b) The particle will accelerate in the direction perpendicular to the field. c) The particle will accelerate in the direction parallel to the field. d) The particle will accelerate in the direction opposite to the field. e) The particle will move with constant velocity in the direction of the field.
a) The particle will not begin to move.
. A transformer has two coils. Coil A has 75 turns and coil B has 100 turns. In the first instance, coil A is used as the primary coil, which is connected to an ac current source. As a result, the peak voltage of the secondary coil, B, has a value VP. Then, coil B is used as the primary coil and coil A becomes the secondary coil. The ac current source is then adjusted to deliver the same current to coil B as it did to coil A in the first instance. For this case, how does the peak voltage of the secondary coil, A, compare with VP. a) The peak voltage of A is VP. b) The peak voltage of A is 1.25VP. c) The peak voltage of A is 0.75VP. d) The peak voltage of A is 1.33VP. e) The peak voltage of A is 0.80VP.
a) The peak voltage of A is VP.
A capacitor is connected to an alternating current power supply. If the capacitor is replaced with another that has a larger capacitance, what is the effect on the rms current in the circuit and the capacitive reactance? a) The rms current will increase as the capacitive reactance decreases. b) The rms current will remain at its initial value as the capacitive reactance decreases. c) The rms current will decrease as the capacitive reactance decreases. d) The rms current will increase as the capacitive reactance increases. e) The rms current will increase as the capacitive reactance decreases.
a) The rms current will increase as the capacitive reactance decreases.
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? a) clockwise b) counterclockwise c) No current is induced.
a) clockwise
There are many devices that utilize the effects of a magnetic field on a current carrying wire. Which one of the following devices does not rely on these effects for its operation? a magnetohydrodynamic (MHD) ship an electric toaster an electric motor a loudspeaker
an electric toaster
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 φ 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 is decreased A is increased φ is decreased ...any of the above choices ...none of the above choices
any of the above choices
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. a) 0.021 V b) 0.031 V c) 0.047 V d) 0.058 V e) 0.075 V
b) 0.031 V
A permanent magnet is moved toward and away from a solenoid with a frequency of 60 Hz. The ends of the solenoid are connected in series with a light bulb. Which one of the following statements concerning an induced current, if any, in the loop is true? a) An alternating current will be induced in the circuit that is clockwise when the magnet moves to the right and counterclockwise when the magnet moves to the left. b) An alternating current will be induced in the circuit that is clockwise when the magnet moves to the left and counterclockwise when the magnet moves to the right. c) An direct current will be induced in the circuit that is clockwise as the magnet oscillates to the left and to the right. d) An direct current will be induced in the circuit that is counterclockwise as the magnet oscillates to the left and to the right. e) No current will be induced in the circuit by using this method.
b) An alternating current will be induced in the circuit that is clockwise when the magnet moves to the left and counterclockwise when the magnet moves to the right.
Three long, straight, identical wires are inserted one at a time into a magnetic field directed due east. Wire A carries a current of 2 A in the direction of 45° south of east. Wire B carries a current of 8 A, due north. Wire C carries a current of 10 A, due west. Rank the wires in terms of the magnitude of the magnetic force on each wire, with the largest force listed first and the smallest force listed last. a) A > B > C b) B > A > C c) C > B > A d) A > C > B e) B > C > A
b) B > A > C
In each of the three cases shown, a time-varying current is flowing through the larger coil that produces a magnetic field. Rank the mutual inductance for the three cases shown from smallest to largest. a) MA< MB< MC b) MC< MB< MA c) MC< MA< MB d) MB< MC< MA e) MB< MA< MC
b) MC< MB< MA
Circuit A contains a battery, a switch, and a resistor connected in series. Circuit B contains a battery, a switch, an inductor, and a resistor connected in series. Initially, the switch is closed in both circuits. How does the behavior of the current in circuit B compare with that in circuit A as both switches are opened at the same time? (The circuits do not influence each other.) a) The current in both circuits decreases at the same rate because inductors do not affect the current in a circuit. b) The current in circuit B decreases more slowly than that for circuit A since the inductor acts to maintain the current in the circuit. c) The current in circuit B decreases more quickly than that for circuit A since the inductor increases the current in the circuit as its stored energy is released. d) The behavior of the current in the circuit depends on the inductance of the inductor. If the inductance is small, the current will decrease rapidly; and if the inductance is large, the current will increase for a short time before decreasing.
b) The current in circuit B decreases more slowly than that for circuit A since the inductor acts to maintain the current in the circuit.
Consider the two rectangular areas shown with a point P located at the midpoint between the two areas. The rectangular area on the left contains a bar magnet with the south pole near point P. The rectangle on the right is initially empty. How will the magnetic field at P change, if at all, when a second bar magnet is placed on the right rectangle with its north pole near point P? a) The direction of the magnetic field will not change, but its magnitude will decrease. b) The direction of the magnetic field will not change, but its magnitude will increase. c) The magnetic field at P will be zero tesla. d) The direction of the magnetic field will change and its magnitude will increase. e) The direction of the magnetic field will change and its magnitude will decrease.
b) The direction of the magnetic field will not change, but its magnitude will increase.
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? a) Wire A attracts wire B with half the force that wire B attracts wire A. b) Wire A attracts wire B with twice the force that wire B attracts wire A. c) Both wires repel each other with the same amount of force. d) Wire A repels wire B with half the force that wire B attracts wire A. e) Wire A repels wire B with twice the force that wire B attracts wire A.
c) Both wires repel each other with the same amount of force.
The coils of a solenoid are stretched so that the length of the solenoid is twice its original length. Assuming the same current is passed though the solenoid before and after it is stretched, how does the magnetic field inside the solenoid change, if at all, as a result of the stretching? a) The magnetic field after the stretching is one-fourth the value it was before stretching. b) The magnetic field after the stretching is one-half the value it was before stretching. c) The magnetic field after the stretching is the same as the value it was before stretching. d) The magnetic field after the stretching is twice the value it was before stretching. e) The magnetic field after the stretching is four times the value it was before stretching.
b) The magnetic field after the stretching is one-half the value it was before stretching.
An alpha particle (a helium nucleus which has a net positive charge) is moving due east when it enters a magnetic field that is directed due north. Which one of the following statements best describes the motion of the alpha particle after entering the magnetic field? a) The particle decelerates while traveling along a straight line until it stops. b) The particle continues at a constant speed, but its direction changes as it follows a circular path. c) The particle continues at a constant speed, but its direction changes as it follows a parabolic path. d) The particle slows and changes direction to accelerate to move due north. e) The particle slows and changes direction to accelerate to move directly upward.
b) The particle continues at a constant speed, but its direction changes as it follows a circular path.
The equation for the magnetic field of a straight, current carrying wire is given by , but the magnetic field at the center of a single closed circular loop is given by . Although these equations look similar, there is an important difference between these two equations, other that the factor of p. What is it? a) The µ0 factor is different for the two situations. b) The variable r represents two different lengths. c) The I represents two different types of current.
b) The variable r represents two different lengths.
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 entering the magnetic field, what will be the direction of any induced current present in the loop? a) clockwise b) counterclockwise c)No current is induced
b) counterclockwise
A charged particle is moving through a constant magnetic field. Does the magnetic field do work on the charged particle? a) yes, because the force is acting as the particle is moving through some distance b) no, because the magnetic force is always perpendicular to the velocity of the particle c) no, because the magnetic field is a vector and work is a scalar quantity d) no, because the magnetic field is conservative e) no, because the magnetic force is a velocity-dependent force
b) no, because the magnetic force is always perpendicular to the velocity of the particle
The drawing shows one type of electric generator. An aluminum disc is rotated with a portion near the edge in between the poles of a powerful C-shaped magnet. As the disc rotates, two metal brushes contact it, one near the outer radius, and one near the center as shown. A voltmeter measures the potential difference between the two brushes. How does this generator produce this potential difference? a) A current appears in the disc to oppose the magnetic field of the magnet. b) The rubbing of the brushes releases electrons from the aluminum and collect near the outer radius of the disc. c) Because the disc is rotating, free electrons in the plate experience a magnetic force that causes them to move toward the outer radius, thus creating a potential difference. d) The magnet exerts a force on free electrons in the aluminum that causes them to move toward the center of the disc, thus creating a potential difference.
c) Because the disc is rotating, free electrons in the plate experience a magnetic force that causes them to move toward the outer radius, thus creating a potential difference.
An electron is traveling due south in a region of space at a constant speed. What can you conclude from this situation regarding the presence any electric and/or magnetic fields? a) The electric field must be zero, but the magnetic field might be non-zero in the region. b) The magnetic field must be zero, but the electric field might be non-zero in the region. c) Both the electric and magnetic field might be non-zero, but if so, they are perpendicular to each other in the region. d) Both the electric and magnetic field might be non-zero, but if so, the fields point in opposite directions in the region. e) Both the electric and magnetic field must be zero in the region.
c) Both the electric and magnetic field might be non-zero, but if so, they are perpendicular to each other in the region.
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? a) Wire A attracts wire B with half the force that wire B attracts wire A. b) Wire A attracts wire B with twice the force that wire B attracts wire A. c) Both wires attract each other with the same amount of force. d) Wire A repels wire B with half the force that wire B attracts wire A. e) Wire A repels wire B with twice the force that wire B attracts wire A.
c) Both wires attract each other with the same amount of force.
Complete the following sentence: When a negatively-charged particle is moving at a constant velocity due east and enters in a region that has a magnetic field directed due east, the particle will be accelerated downward. be accelerated upward. be accelerated due west. be accelerated due east. continue moving due east at constant velocity.
continue moving due east at constant velocity.
Two rods are resting on a table. Although they appear to be identical, one is a permanent magnet and the other is made from soft iron and is not permanently magnetized. Which one of the following methods is most likely to reveal which rod is the magnet and which is the soft iron? a) Take one of the rods and touch it to each end of the other rod. b) Use a magnetic monopole to find the end of one of the rods that repels it. c) Move a compass along each rod to see if the compass needle behaves as it should in a magnetic field. d) There is no way to tell the difference between the two rods.
c) Move a compass along each rod to see if the compass needle behaves as it should in a magnetic field.
A rigid, circular metal loop begins at rest in a uniform magnetic field directed away from you as shown. The loop is then pulled through the field toward the right, but does not exit the field. What is the direction of any induced current within the loop? a) clockwise b) counterclockwise c) No current is induced.
c) No current is induced.
Transformer A has a primary coil with 400 turns and a secondary coil with 200 turns. Transformer B has a primary coil with 400 turns and a secondary coil with 800 turns. The same current and voltage are delivered to the primary coil of both transformers. The secondary coils are connected to identical circuits. How does the power delivered by secondary coil A compare to the power delivered by secondary coil B? a) Secondary coil A delivers one fourth the power delivered by secondary coil B b) Secondary coil A delivers one half the power delivered by secondary coil B c) Secondary coil A delivers the same power as delivered by secondary coil B d) Secondary coil A delivers twice the power delivered by secondary coil B e) Secondary coil A delivers four times the power delivered by secondary coil B
c) Secondary coil A delivers the same power as delivered by secondary coil B
Consider the two rectangular areas shown with a point P located at the midpoint between the two areas. The rectangular area on the left contains a bar magnet with the south pole near point P. The rectangle on the right is initially empty. How will the magnetic field at P change, if at all, when a second bar magnet is placed on the right rectangle with its south pole near point P? a) The direction of the magnetic field will not change, but its magnitude will decrease. b) The direction of the magnetic field will not change, but its magnitude will increase. c) The magnetic field at P will be zero tesla. d) The direction of the magnetic field will change and its magnitude will increase. e) The direction of the magnetic field will change and its magnitude will decrease.
c) The magnetic field at P will be zero tesla.
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) before the switch is closed b) immediately after the switch is closed when the current in the circuit is increasing c) a long time after the switch is closed
c) a long time after the switch is closed
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? a) upward, away from the earth b) downward, toward the earth c) due north d) due west e) due south
c) due north
Complete the following sentence: The phenomenon of producing an induced emf with the aid of a magnetic field is called electromagnetic induction. almost never observed. called electromotive production. a scientific curiosity with no practical application. only produced by changing the magnetic field in the presence of a coil of wire.
called electromagnetic induction.
Lenz's law is a consequence of what other physical law? Newton's third law conservation of energy Gauss' law conservation of momentum Newton's first law
conservation of energy
The drawing illustrates an electric generator in which there are two independent loops that are oriented perpendicular to one another. As the generator rotates, the loops in turn make contact with the circuit shown for nearly one fourth of a revolution and the light bulb is illuminated. Which one of the graphs shown below best represents the voltage generated by this generator as a function of time?
d
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? a) 47 V b) 1.6 V c) 5.7 V d) .82 V e) 0.051 V
d) .82 V
. Which one of the following statements concerning the magnetic force on a charged particle in a magnetic field is true? a) The magnitude of the force is largest when the particle is not moving. b) The force is zero if the particle moves perpendicular to the field. c) The magnitude of the force is largest when the particle moves parallel to the direction of the magnetic field. d) The force depends on the component of the particle's velocity that is perpendicular to the field. e) The force acts in the direction of motion for a positively charged particle.
d) The force depends on the component of the particle's velocity that is perpendicular to the field.
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? a) A magnetic force accelerates the bar to the right. b) Since the bar is unmagnetized, there will not be any affect on the bar. c) The magnetic field of the solenoid will cause a current to flow in a loop that extends from one end of the bar to the other and that continues until the battery is disconnected from the solenoid. d) The magnetic field of the solenoid induces magnetism in the bar with the bar's north pole nearest to the solenoid. e) The magnetic field of the solenoid induces magnetism in the bar with the bar's south pole nearest to the solenoid.
d) The magnetic field of the solenoid induces magnetism in the bar with the bar's north pole nearest to the solenoid.
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? a) The wire moves toward the north pole of the magnet. b) The wire moves toward the south pole of the magnet. c) The wire moves upward (toward us, out of the plane of the diagram). d) The wire moves downward (away from us, into the plane of the diagram). e) The wire doesn't move.
d) The wire moves downward (away from us, into the plane of the diagram).
A rectangular loop of wire is attached to a metal rod using rigid, electrically insulating rods so that the distance between the loop and metal rod is constant as the metal rod is rotated uniformly as shown. The metal rod carries a constant current in the direction indicated. Which of the following statements concerning an induced current in the rectangular loop as a result of the current in the metal rod is true? a) The induced current in the loop is clockwise around the loop. b) The induced current in the loop is counterclockwise around the loop. c) The induced current in the loop alternates between clockwise and counterclockwise around the loop. d) There is no induced current in the loop.
d) There is no induced current in the loop.
The drawing represents a device called Roget's Spiral. A coil of wire hangs vertically and its windings are parallel to one another. One end of the coil is connected by a wire to a terminal of a battery. The other end of the coil is just slightly submerged below the surface of a cup of mercury. Mercury is a liquid metal at room temperature. The bottom of the cup is also metallic and connected by a wire to a switch. A wire from the switch to the battery completes the circuit. What is the behavior of this circuit after the switch is closed? a) When current flows in the circuit, the coils of the wire move apart and the wire is extended further into the mercury. b) Nothing happens to the coil because there will not be a current in this circuit. c) A current passes through the circuit until all of the mercury is boiled away. d) When current flows in the circuit, the coils of the wire move together, causing the circuit to break at the surface of the mercury. The coil then extends and the process begins again when the circuit is once again complete.
d) When current flows in the circuit, the coils of the wire move together, causing the circuit to break at the surface of the mercury. The coil then extends and the process begins again when the circuit is once again complete.
You are given a bar magnet, but the poles are not labeled. Using which of the following items can you determine which end is a north pole and which is a south pole? a) a voltmeter b) a bottle of iron particles c) a charged rubber rod d) a compass e) a steel rod
d) a compass
How is the direction of a magnetic field at a location indicated? a. A magnetic field is always directed directly opposite to the direction that the north pole of a small compass needle points at the location. b. A magnetic field is always directed perpendicular and vertically upward from the direction that the north pole of a small compass needle points at the location. c. A magnetic field is always directed perpendicular and vertically downward from the direction that the north pole of a small compass needle points at the location. d. A magnetic field is always directed in the direction that the north pole of a small compass needle points at the location. e. A magnetic field is always directed toward due north.
d. A magnetic field is always directed in the direction that the north pole of a small compass needle points at the location.
You are looking in the direction of the magnetic field in a specific region as shown. A square, metal loop is moving from left to right at a constant speed. Which one of the graphs below shows the behavior of the current in the loop as the loop passes into and then out of the magnetic field?
e
Five identical capacitors are connected in three different circuits as shown. The ac current source in each circuit is the same. In which circuit is the rms current the largest and in which is the rms current the smallest? a) C has the largest rms current and A has the smallest. b) A has the largest rms current and C has the smallest. c) B has the largest rms current and A has the smallest. d) B has the largest rms current and C has the smallest. e) C has the largest rms current and B has the smallest.
e) C has the largest rms current and B has the smallest.
A potential difference exists between the ends of an inductor. At the instant shown, the upper end is at a higher potential than the lower end. Which one of the following statements accurately describes the current in the inductor? a) The current has a constant value and is directed from the top of the inductor toward the bottom of the inductor. b) The current is increasing and is directed from the top of the inductor toward the bottom of the inductor. c) The current is decreasing and is directed from the top of the inductor toward the bottom of the inductor. d) The current is increasing and is directed from the bottom of the inductor toward the top of the inductor. e) The current may be increasing and directed from the top toward the bottom or decreasing and directed from the bottom toward the top of the inductor.
e) The current may be increasing and directed from the top toward the bottom or decreasing and directed from the bottom toward the top of the inductor.
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 by the magnetic field is true? a) The force is directed perpendicular to the magnetic field. b) The force is perpendicular to the direction in which the particle is moving. c) The force slows the particle. d) The force accelerates the particle. e) The force has a magnitude of zero newtons.
e) The force has a magnitude of zero newtons.
The drawing shows a rectangular wire loop that has one side passing through the center of a solenoid. Which one of the following statements describes the force, if any, that acts on the rectangular loop when a steady current is passing through the solenoid. a) The magnetic force causes the loop to move upward. b) The magnetic force causes the loop to move downward. c) The magnetic force causes the loop to move to the right. d) The magnetic force causes the loop to move to the left. e) The loop is not affected by the current passing through the solenoid or the magnetic field resulting from it.
e) The loop is not affected by the current passing through the solenoid or the magnetic field resulting from it.
A rigid, conductive loop is falling through a uniform magnetic field that is perpendicular to the plane of the loop. Initially, the loop is completely within the field, but then it falls into a region where no magnetic field is present. Which one of the following quantities varies during the fall? a) the magnetic field penetrating the loop b) the area of the loop penetrated by the magnetic field c) the magnetic flux d) the current in the loop e) all of the above
e) all of the above
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?
e) zero tesla
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? zero percent twenty-five percent fifty percent seventy-five percent ten percent
fifty percent
Which one of the following parameters is not used to determine the magnetic force on a current-carrying wire in a magnetic field? direction of the magnetic field with respect to the direction of the current the magnitude of the electric current the strength of the magnetic field length of the wire radius of the wire
radius of the wire
Complete the following sentence: When a positively-charged particle is released from rest in a region that has a magnetic field directed due east, the particle will be accelerated upward. remain at rest. be accelerated due north. be accelerated due east. be accelerated downward.
remain at rest.
Which of the following types of waves is not part of the electromagnetic spectrum? microwaves gamma rays radio waves sound waves ultraviolet radiation
sound waves
Complete the following sentence: In a coil of wire, the direction of the induced current caused by an increasing magnetic flux is directed in the direction of the original magnetic field. such that the induced magnetic field increases the magnetic flux. a current directed opposite to the original magnetic field. such that the net magnetic flux is equal to zero webers. such that the induced magnetic field decreases the magnetic flux.
such that the induced magnetic field decreases the magnetic flux.
Which of the following phrases best describe the term magnetic flux? the amount of magnetic current in a wire the flow of magnet monopoles in space the number of magnetic dipoles moving through a wire the amount of magnetic field that passes through a surface the direction of the magnetic field relative to a surface
the amount of magnetic field that passes through a surface
Complete the following statement: The polarization direction of an electromagnetic wave is determined by the wavelength of the electromagnetic radiation. the direction of the magnetic field component. the frequency of the electromagnetic radiation. the direction the wave is traveling. the direction of the electric field component.
the direction of the electric field component.
A long wire, parallel to the ground, 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? vertically downward west east north vertically upward
west
Which one of the following types of electromagnetic radiation is produced by the sudden deceleration of high speed electrons? x-rays infrared radiation visible light gamma rays microwaves
x-rays
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 remains constant no, the magnetic flux remains constant yes, the magnetic flux increases no, the magnetic flux increases no, the magnetic flux decreases
yes, the magnetic flux increases
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? seventy-five percent ten percent fifty percent twenty-five percent zero percent
zero percent