Physics MC exam 3
The equivalent resistance of 2 identical resistors with resistance R, which are connected in series is R/2 Unknown. There is not enough information here. 2R Depends on the type of resistor
2R
How many time constants does it take to discharge a capacitor in an RC circuit? Never fully discharged but 5 is accepted as the time it takes 3 2 10
Never fully discharged but 5 is accepted as the time it takes
What is the equivalent resistance when R1, R2 and R3 are all connected in series? 1/R1 + 1/R2+ 1/R3 R1+R2+R3 (R1*R2)/R3 R1+R2-R3
R1+R2+R3
The magnetic field of a solenoid does not depend on The radius of the solenoid The number of turns of wire The length of the solenoid The current in the wire
The radius of the solenoid
The parts of the electromagnetic spectrum that can ionize molecules and/or atoms are Ultraviolet only X-rays and gamma rays only Ultraviolet, x-rays and gamma rays Infrared and visible light
Ultraviolet, x-rays and gamma rays
To measure the potential difference at a circuit element a voltmeter must be connected In series with an ammeter In parallel with the element to be tested In series with the circuit elements Any way you want.
In parallel with the element to be tested
To measure current in a circuit the ammeter must be connected In parallel with the battery In parallel with the resistor In series with the circuit elements Any way you want.
In series with the circuit elements
The Earth's magnetic north pole is Perfectly aligned with the Earth's north geographic pole Near Earth's south geographic pole Perfectly aligned with the Earth's south geographic pole Near Earth's north geographic pole
Near Earth's south geographic pole
Eddy currents are only produced By moving a conductor in a magnetic field In magnetic materials By changing the magnetic field None of these are correct.
None of these are correct.
The north pole of a magnet attracts Stationary protons Stationary electrons and protons None of these are true Stationary electrons
None of these are true
Video 2: When the north pole of the magnet moves toward the copper a magnetic field is induced in the copper. What direction is the force between the copper and the magnet? There is no force - copper is not magnetic Attractive Repulsive
Repulsive
Which circuit element has a zigzag for its symbol? Capacitor Resistor Battery Light bulb
Resistor
Kirchhoff's loop law Says the potential difference around a loop depends on the direction of the current Says the total potential difference around a loop is positive Says the potential difference around a loop is zero Says the total potential difference around a loop is negative
Says the potential difference around a loop is zero
In a circuit model of nerve-impulse propagation, what would happen to the propagation speed if the myalin sheath thickness were larger? No change Speed would decrease Speed would increase Not enough information
Speed would increase
Computer hard disks Store data using magnetic fields Store data using electric fields Create a current in the computer Are not discussed in this chapter.
Store data using magnetic fields
Changing the angle of a wire loop relative to a magnetic field changes Nothing The magnetic flux The size of the loop The magnetic field
The magnetic flux
Faraday's law of electromagnetic induction helps determine The direction of induced currents and emfs. The direction and magnitude of induced currents only The magnitude of induced emfs and currents The direction and magnitude of induced emfs only
The magnitude of induced emfs and currents
What is the equivalent resistance when R1, R2, and R3 are all connected in parallel? 1/R1 + 1/R2+ 1/R3 R1+ 1/R2 + 1/R3 R1(R2/R3) (1/R1 + 1/R2+ 1/R3)-1
1/R1 + 1/R2+ 1/R3
What is the current in a circuit with a 10 V battery and 1000 ohms of resistance? 10 mA 100 mA 1A None of these are correct 1 mA
10 mA
When the resistors are connected in 2 loops (first circuit of the video) the current through the resistors are 1 mA and 10mA. What is the current in the circuit before the junction that splits to the 2 resistors? 10 mA 11 mA 9 mA 1 mA
11 mA
A circuit consists of 1 battery and 2 identical resistors connected in parallel to the battery. The battery has an emf of 12 V. What is the potential difference across the first resistor? Not enough information to answer 12 V 24 V 6 V
12 V
A circuit consists of 1 battery and 2 identical resistors connected in series with the battery. The battery has an emf of 12 V. What is the potential difference across both resistors? 24 V 12 V Not enough information to answer 6 V
12 V
Induced current is current created by A very strong constant magnetic field A changing magnetic field Moving a circuit in an electric field A changing electric field
A changing magnetic field
Two current carrying wires parallel to each other exert Only an attractive force A repulsive or attractive force depending on the directions of the currents Only a repulsive force No force on each other
A repulsive or attractive force depending on the directions of the currents
A resistor, an uncharged capacitor, a dc voltage source, and an open switch are all connected in series. The switch is closed at time t = 0 s. Which one of the following is a correct statement about this circuit? A) The charge on the capacitor after four time constants is about 98% of the maximum value. B) The charge on the capacitor after one time constant is 50% of its maximum value. C) The charge on the capacitor after one time constant is 1/e of its maximum value. D) The voltage on the capacitor after one time constant is 1/e of the maximum value. E) The voltage on this capacitor after one time constant is 100% of its maximum value.
A) The charge on the capacitor after four time constants is about 98% of the maximum value.
Four unequal resistors are connected in a parallel with each other. Which one of the following statements is correct about this combination? A) The equivalent resistance is less than that of the smallest resistor. B) The equivalent resistance is equal to the average of the four resistances. C) The equivalent resistance is midway between the largest and smallest resistance. D) The equivalent resistance is more than the largest resistance. E) None of the other choices is correct.
A) The equivalent resistance is less than that of the smallest resistor.
An object is hung using a metal spring. If now a current is passed through the spring, what will happen to this system? A) The spring will contract, raising the weight. B) The spring will extend, lowering the weight. C) The weight will not move. D) The spring will begin to swing like a pendulum. E) None of these are true.
A) The spring will contract, raising the weight.
An electromagnetic wave is propagating towards the west in free space. At a certain moment the direction of the magnetic field vector associated with this wave points vertically upward. What is the direction of the electric field vector? A) horizontal and pointing south B) vertical and pointing down C) horizontal and pointing north D) vertical and pointing upward E) horizontal and pointing east
A) horizontal and pointing south
Increasing the brightness of a beam of light without changing its color will increase A) the number of photons per second traveling in the beam. B) the energy of each photon. C) the speed of the photons. D) the frequency of the light. E) the wavelength of the photons.
A) the number of photons per second traveling in the beam.
When two or more different capacitors are connected in series across a potential source, which of the following statements must be true? (There could be more than one correct choice.) A) The total voltage across the combination is the algebraic sum of the voltages across the individual capacitors. B) Each capacitor carries the same amount of charge. C) The equivalent capacitance of the combination is less than the capacitance of any of the capacitors. D) The potential difference across each capacitor is the same. E) The capacitor with the largest capacitance has the most charge.
A, B, C
When two or more different capacitors are connected in parallel across a potential source (battery), which of the following statements must be true? (There could be more than one correct choice.) A) The potential difference across each capacitor is the same. B) Each capacitor carries the same amount of charge. C) The equivalent capacitance of the combination is less than the capacitance of any one of the capacitors. D) The capacitor with the largest capacitance has the largest potential difference across it. E) The capacitor with the largest capacitance has the most charge
A, E
Several capacitors are connected in series with a battery. The potential difference across each capacitor Continues to change after the capacitors are fully charged Is the same for all the capacitors Adds to equal the emf of the battery Is always largest for the first capacitor in the series
Adds to equal the emf of the battery
The electric field and magnetic field of an electromagnetic wave All of these are correct. Are perpendicular Are related to the speed of light Are in phase with each other
All of these are correct.
Which element listed below is ferromagnetic? All of these are ferromagnetic Cobalt Nickel None of these are ferromagnetic Iron
All of these are ferromagnetic
Which of these is not a way to create a changing magnetic field? Opening or closing a switch in a circuit Moving a magnet relative to a circuit Moving a circuit relative to a magnet All of these create a changing magnetic field.
All of these create a changing magnetic field.
RC circuits can be used for All of these use RC circuits Intermittent wipers on your car Flashing lights on bicycles Timing in computers
All of these use RC circuits
How are radio waves created? Not discussed in this chapter An oscillating dipole causes an oscillating electric field which induces an oscillating magnetic field An oscillating dipole causes an oscillating magnetic field which induces an oscillating electric field An oscillating dipole creates oscillating magnetic and electric fields at the same time.
An oscillating dipole causes an oscillating electric field which induces an oscillating magnetic field
Two parallel loops of wire with current moving in the same direction are near each other with an imaginary line connecting the centers of both loops and passing through the loops. What is the force between them? Attractive Repulsive It depends on the amount of current There is no force
Attractive
Current in a wire creates a magnetic field Only if the wire is magnetic In the direction opposite the current Around the wire Only if the wire is straight
Around the wire
What magnetic field, B, is needed to create a motional emf for a conductor moving at speed v that is d long. B = emf*v*d B = emf*d/v B = emf/(vd) B = vd/emf
B = emf/(vd)
How does the magnetic field, B, of a current carrying wire depend on the current, I, and the distance, r, from the wire? B ∝ I/r B ∝ rI B ∝ r/I B ∝ 1/rI
B ∝ I/r
Two long, parallel wires carry currents of different magnitudes. If the current in one of the wires is doubled and the current in the other wire is halved, what happens to the magnitude of the magnetic force that each wire exerts on the other? A) It is doubled. B) It stays the same. C) It is tripled. D) It is quadrupled. E) It is reduced by a factor of two.
B) It stays the same.
When the switch is closed in the circuit shown in the figure, the wire between the poles of the horseshoe magnet deflects upward. From this you can conclude that the left end of the magnet is A) a north magnetic pole. B) a south magnetic pole. C) There is not enough information given to answer the question.
B) a south magnetic pole.
A coil lies flat on a level tabletop in a region where the magnetic field vector points straight up. The magnetic field suddenly grows stronger. When viewed from above, what is the direction of the induced current in this coil as the field increases? A) counterclockwise B) clockwise C) clockwise initially, then counterclockwise before stopping D) There is no induced current in this coil.
B) clockwise
A bar magnet is oriented above a copper ring, as shown in the figure. If the magnet is pulled upward, what is the direction of the current induced in the ring, as viewed from above? A) There is no current in the ring. B) counterclockwise C) clockwise
B) counterclockwise
An outer metal ring surrounds an inner metal ring, as shown in the figure. The current in the outer ring is counterclockwise and decreasing. What is the direction of the induced current in the inner ring? A) clockwise B) counterclockwise C) There is no induced current in the inner ring.
B) counterclockwise
The force needed to pull a wire along conducting rails in a magnetic field is proportional to B^2 None of the above R B
B^2
An electromagnetic flowmeter can be used to measure the velocity of Water in a river Blood in an artery Blood and water None of these
Blood and water
Magnetic domains are usually randomly oriented. This can be changed by Bringing a magnet close to the sample Hitting the sample with a hammer Heating the sample Cooling the sample
Bringing a magnet close to the sample
When two long parallel wires carry unequal currents, the magnitude of the magnetic force that one wire exerts on the other is F. If the current in both wires is now doubled, what is the magnitude of the new magnetic force on each wire? A) 16F B) 8F C) 4F D) 2F E) F√2
C) 4F
Which one of the following statements is correct? A) Earth's geographic north pole is the north pole of Earth's magnetic field. B) Earth's geographic south pole is the south pole of Earth's magnetic field. C) The north pole of a magnet points towards Earth's geographic north pole. D) The north pole of a magnet points towards Earth's geographic south pole. E) None of the above statements is correct.
C) The north pole of a magnet points towards Earth's geographic north pole.
A negatively-charged particle moves across a constant uniform magnetic field that is perpendicular to the velocity of the particle. The magnetic force on this particle A) causes the particle to speed up. B) causes the particle to slow down. C) causes the particle to accelerate. D) is in the same direction as the particle's velocity E) is opposite the direction of the particle's velocity.
C) causes the particle to accelerate.
In an electromagnetic wave in free space, the electric and magnetic fields are A) parallel to one another and perpendicular to the direction of wave propagation. B) parallel to one another and parallel to the direction of wave propagation. C) perpendicular to one another and perpendicular to the direction of wave propagation. D) perpendicular to one another and parallel to the direction of wave propagation.
C) perpendicular to one another and perpendicular to the direction of wave propagation.
A flat coil is in a uniform magnetic field. The magnetic flux through the coil is greatest when the plane of its area is A) parallel to the magnetic field. B) at 45° with the magnetic field. C) perpendicular to the magnetic field.
C) perpendicular to the magnetic field.
Kirchhoff's loop rule is a statement of A) the law of conservation of momentum. B) the law of conservation of charge. C) the law of conservation of energy. D) the law of conservation of angular momentum. E) Newton's second law.
C) the law of conservation of energy.
What is the equivalent capacitance for capacitors C1, C2, and C3 when they are connected in parallel? (C1C2+C2C3)/(C1C2C3) [(1/C1) + (1/C2) + (1/C3)]-1 (1/C1) + (1/C2) + (1/C3) C1+C2+C3
C1+C2+C3
Cell walls can be modeled as what electric element(s)? Capacitors and resistors Capacitors Resistors None. Cells don't have electrical properties
Capacitors and resistors
The auroras near Earth's north and south poles are created by The auroras are not discussed in this chapter. Clouds interaction with Earth's magnetic field Lightning interacting with Earth's magnetic field Charged particle from the sun interacting with Earth's magnetic field
Charged particle from the sun interacting with Earth's magnetic field
Which animal has 4 types of cones in their eyes? Chicken Bee Dog Mouse
Chicken
A changing electric field Affects nothing Stops all currents Creates an induced magnetic field Creates magnetic monopoles
Creates an induced magnetic field
Kirchhoff's junction law states that Current leaving a junction is less than current entering it Current into a junction is equal to current leaving it Current cannot split at a junction Current entering a junction is less than current leaving it
Current into a junction is equal to current leaving it
Consider two current-carrying circular loops. Both are made from one strand of wire and both carry the same current, but one has twice the radius of the other. If the magnetic field strength at the center of the smaller loop is B, what is the magnetic field strength at the center of the larger loop? A) 8B B) 4B C) 2B D) B/2 E) B/4
D) B/2
You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in the normal way, you devise a circuit that places them in series across normal household voltage. If each one is an incandescent bulb of fixed resistance, which statement about these bulbs is correct? A) Both bulbs glow with the same brightness, but less than their normal brightness. B) Both bulbs glow with the same brightness, but more than their normal brightness. C) The 100-W bulb glows brighter than the 50-W bulb. D) The 50-W bulb glows more brightly than the 100-W bulb
D) The 50-W bulb glows more brightly than the 100-W bulb
You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in the normal way, you devise a circuit that places them in series across normal household voltage. If each one is an incandescent bulb of fixed resistance, which statement about these bulbs is correct? A) Both bulbs glow with the same brightness, but less than their normal brightness. B) Both bulbs glow with the same brightness, but more than their normal brightness. C) The 100-W bulb glows brighter than the 50-W bulb. D) The 50-W bulb glows more brightly than the 100-W bulb.
D) The 50-W bulb glows more brightly than the 100-W bulb.
Which one of the following lists gives the correct order of the electromagnetic waves from longer wavelength to shorter wavelength? A) radio waves, infrared, microwaves, ultraviolet, visible, x-rays, gamma rays B) radio waves, ultraviolet, x-rays, microwaves, infrared, visible, gamma rays C) radio waves, microwaves, visible, x-rays, infrared, ultraviolet, gamma rays D) radio waves, microwaves, infrared, visible, ultraviolet, x-rays, gamma rays E) radio waves, infrared, x-rays, microwaves, ultraviolet, visible, gamma rays
D) radio waves, microwaves, infrared, visible, ultraviolet, x-rays, gamma rays
The exponential behavior of an RC circuit occurs Only for certain ratios of R to C Only when the capacitor is charging During charging and discharging of the capacitor Only when the capacitor is discharging
During charging and discharging of the capacitor
Which of these equations is correct for the energy of a photon? E = hλ E = cf E = hf/c E = hf
E = hf
Four unequal resistors are connected in series with each other. Which one of the following statements is correct about this combination? A) The equivalent resistance is equal to that of any one of the resistors. B) The equivalent resistance is equal to average of the four resistances. C) The equivalent resistance is less than that of the smallest resistor. D) The equivalent resistance is less than that of the largest resistor. E) The equivalent resistance is more than the largest resistance.
E) The equivalent resistance is more than the largest resistance.
What is the magnetic force, F, on a wire of length L carrying current I, in a magnetic field B? F = IL/B F = B/IL F = 1/ILB F = ILB
F = ILB
Magnetic field lines point from Positive electric poles to negative electric poles From north magnetic poles to south magnetic poles Negative electric poles to positive electric poles From south magnetic poles to north magnetic poles
From north magnetic poles to south magnetic poles
Video 1: What is the property of the copper in the track that leads to the braking force on the toy car? Good electrical conductor Copper is magnetic Friction Good thermal conductor
Good electrical conductor
Refrigerator magnets Have multiple poles arranged as long U-magnets Aren't really magnets. Have strong magnetic fields on both sides Are flexible bar magnets
Have multiple poles arranged as long U-magnets
The induced current, I, due to an induced emf is I = emf*R None of these are correct I = emf/R I = R/emf
I = emf/R
The speed of an electromagnetic wave Depends on the wavelength Depends on the angle between the electric and magnetic fields Depends on the frequency Is equal to the speed of light
Is equal to the speed of light
The magnetic field inside a current loop Is in the same direction as the field outside the loop Does not exist. Is in the opposite direction as the field outside the loop Is weaker than the field outside the loop
Is in the opposite direction as the field outside the loop
The magnetic field of a solenoid Is stronger outside the solenoid than inside Is in the direction of the radius of the solenoid Is stronger inside the solenoid than outside Is not in this chapter
Is stronger inside the solenoid than outside
Several capacitors are connected in series with a battery. The charge on the capacitors Does not depend on the emf. Does not depend on the capacitors Is the same for each capacitor Is summed to determine the total charge stored
Is the same for each capacitor
Video 3: How does the flash rate change for the light in the RC circuit when a larger resistor is put into the circuit? It doesn't change It gets slower It alternates between fast and slow. It gets faster
It gets slower
Video 3: What property of the trash can blocks radio waves from getting to the radio? The color It is ferromagnetic. It is a good electrical conductor. The location in the studio.
It is a good electrical conductor.
What law describes the directions of eddy currents produced when a conductor moves through a magnetic field? Faraday Kirchhoff Lenz Ohm
Lenz
The path of a charged object in a magnetic field depends on Its mass Its charge Mass, velocity and charge Its velocity None of these are correct
Mass, velocity and charge
Magnets attract Only other magnets All metals All materials Magnetic materials
Magnetic materials
MRI's use what property of atoms to produce images? Magnetic moment of the electrons Magnetic force between the protons and electrons Magnetic moment of the nucleus Mass of the nucleus
Magnetic moment of the nucleus
A generator converts Mechanical energy into electrical energy Electrical energy into mechanical energy Gravitational energy into mechanical energy Electrical energy into gravitational energy
Mechanical energy into electrical energy
The potential difference created by moving a conductor in a magnetic field is called Kinetic magnetic energy Kinetic electric energy Motional emf Electric potential energy
Motional emf
The induced current due to a changing magnetic flux produces a magnetic field which Reinforces the change of the flux Opposes the change of the flux A changing magnetic field does not induce a current. Is perpendicular to the change of the flux
Opposes the change of the flux
How are car headlights connected? Depends on the type of car Parallel This isn't mentioned in this chapter. Series
Parallel
The force on a moving charged object in a magnetic field is Perpendicular to both the magnetic field and the object's velocity Perpendicular to the magnetic field and parallel to the object's velocity Parallel to both the magnetic field and the object's velocity Parallel to the magnetic field and perpendicular to the object's velocity
Perpendicular to both the magnetic field and the object's velocity
The time constant for an RC circuit is R/C C/R R+C R*C
R*C
The equivalent resistance of 2 identical resistors, with resistance R, which are connected in parallel is 2R Depends on the type of resistor Unknown. There is not enough information here. R/2
R/2
The electromagnetic spectrum consists of X-rays and gamma rays only Infrared, visible and ultraviolet light only Radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays and gamma rays Radio waves and microwaves only
Radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays and gamma rays
Video 2: When current flows in a counterclockwise direction in a current loop the magnetic field created points to the left. What is the field direction when the current is reversed? Right Left
Right
What rule is used to determine the direction of the magnetic field created by a current moving in a wire? Loop rule Right hand rule Left hand rule Junction rule
Right hand rule
What rule is used to determine the force on a current carrying wire due to a magnetic field? Right hand rule Left hand rule There is no force Kirchhoff's loop rule
Right hand rule
A current loop has a magnetic dipole moment equal to The current times the magnetic field The current times the area of the loop The current divided by the area of the loop The magnetic field divided by the current
The current divided by the area of the loop
In a series circuit with 2 resistors The current flows through one resistor then the next The current splits and flows through both resistors at the same time No current flows through the second resistor There is no potential drop across the second resistor
The current flows through one resistor then the next
In order for an electric motor to work The magnetic fields must change polarity every other cycle The current must change direction every half cycle The current must always be in the same direction The direction of the loop must change every cycle
The current must change direction every half cycle
In a parallel resistor circuit with 2 resistors The current flows through one resistor at a time The equivalent resistance is equal to the sum of the resistors The current splits and flows through both resistors at the same time The potential drop across the first resistor is always the largest.
The current splits and flows through both resistors at the same time
Magnetic flux refers to how much magnetic field goes through a loop. The flux depends on the magnetic field and The width of the loop The total area of the loop The length of the loop The effective area of the loop
The effective area of the loop
The polarization of electromagnetic waves refers to the orientation of The electric field The source of the wave The magnetic field None of these are correct
The electric field
Video 3: A cell phone emits EM waves at 1.9 GHz and a microwave oven emits EM waves at 2.4 GHz. Which one emits the shorter wavelength? They emit the same wavelength The microwave oven The cell phone
The microwave oven
Video 2: The circuit is constructed so that the blue LED comes on if the current is in one direction and the orange LED comes on if the current is in the other direction. The blue LED comes on when the magnet is quickly placed on the coil. As the magnet is quickly removed from the coil what will happen? The orange LED comes on. No LED comes on The blue LED comes on Both LED's come on
The orange LED comes on.
A photon is A figment of Einstein's imagination Not in this chapter The particle aspect of an electromagnetic wave A positively charged part of an atomic nucleus
The particle aspect of an electromagnetic wave
The equivalent capacitance of 2 capacitors connected in parallel is The ratio of the smaller divided by the larger The product of the capacitances The sum of the capacitances The ratio of the larger divided by the smaller
The sum of the capacitances
Video 3: Which laser pointer (red or violet) outputs the higher energy photons? The red laser They have the same intensity so the same energy It depends on the width of the beam The violet laser
The violet laser
What direction is the magnetic force on a proton moving in the same direction as a magnetic field? To the right There is no force Down Up To the left
There is no force
When capacitors are connected in series The total capacitance is the sum of the capacitors The current is constant They each see the full voltage of the battery They have the same charge
They have the same charge
Video 3: When looking at the force on the wire with a current, which direction is the force on the wire when subjected to the south pole of the magnet? Current is to the left. Up Down Toward the camera Away from the camera
Toward the camera
Cutting a permanent magnet in half creates Two stronger magnets Two weaker magnets A separate north pole and south pole Two non-magnetic pieces of metal
Two weaker magnets
How do you determine the magnetic force on a negatively charged object moving through a magnetic field? It can't be determined This is not discussed in this chapter Use the right-hand rule Use the right-hand rule and then reverse the direction of the force.
Use the right-hand rule and then reverse the direction of the force.
Which part of the electromagnetic spectrum listed below is the most particle like? Green light Microwaves Infrared light X-rays
X-rays
