Physics 2 final
A beam of electrons moves to the right with speed v� between two conducting plates and parallel to a wire with current I� directed to the right, as shown above. The bottom plate is grounded (VB=0)(��=0), and the top plate has potential VT��. Several values of I� are used. For each value, the potential VT�� of the top plate is adjusted until the beam is undeflected while it is between the plates. A graph of VT�� as a function of I� is shown. The procedure is repeated, but VT�� is fixed and the speed v� of the electrons is adjusted to keep the beam undeflected. Which of the following graphs correctly shows v� as a function of I� for the new procedure? A inverse proportion (decay) B exponential C Linear horizontal D Linear decresing
A
An electron is moving to the right, as shown in the figure above. It passes through the shaded region, which contains a magnetic field. The electron travels along a path that takes it through point P. The gravitational force on the electron is negligible. What is the direction of the magnetic field? A Into the page B Out of the page C Toward the top of the page D Toward the bottom of the page
A
The conducting loop shown above is in a region containing two uniform magnetic fields that point out of the page. The magnitude of the field inside the loop is B1�1, and the magnitude of the field outside the loop is B2�2. The magnitude of each field is decreasing at a constant rate. Which of the following represents the magnetic flux through the loop while the magnitudes of the fields are decreasing? A B1ab�1�� B B2ab�2�� C (B1−B2)ab(�1−�2)�� D (B1+B2)ab
A B1ab�1��
An object with charge +q passes to the right of one pole of a magnet and at a particular instant is moving with a velocity toward the bottom of the page, as shown in the figure above. The force exerted on the object by the magnet at that instant is directed into the page. What is the direction of the force exerted on the magnet by the object? A Out of the page B Toward the right C Toward the top of the page D No direction; the force is zero.
A out of page
A bar magnet is pushed from left to right completely through a loop of metal wire, as shown in the figures above. The two possible directions for current in the loop are also shown. Which of the following indicates the directions of the induced current in the loop, if any, as the magnet is moving through the positions shown? A Figure 1Figure 2Direction 1Direction 1 B Figure 1Figure 2Direction 1Direction 2 C Figure 1Figure 2Direction 2Direction 1 D Figure 1Figure 2Direction 2Direction 2 E Figure 1Figure 2None (no current)None (no current)
B
A circular conducting loop is in a region of magnetic field B directed out of the page, as shown above. The magnitude of the magnetic field is decreasing. The direction of the induced current in the loop is A clockwise B counterclockwise C undefined because the current is zero D impossible to determine without knowingthe rate of change of the field E impossible to determine without knowingthe radius of the loop
B
A group of students wants to determine the internal resistance of a battery. They connect the battery to a variable resistor. The students measure the potential difference across the battery as a function of the current through the battery as they vary the resistance. Which of the following analyses of the data could be used to determine the internal resistance of the battery? A Divide the potential difference across the battery by the current through it for each data point. The average of these calculations gives the internal resistance of the battery. B Graph the potential difference across the battery as a function of the current through it. Extrapolate to find the y-intercept and divide this by the average of the current measurements to find the internal resistance of the battery. C Find the best-fit straight line for a graph of potential difference across the battery as a function of the current through it. The absolute value of the slope represents the internal resistance of the battery. D This data cannot be analyzed to give the internal resistance of the battery, because the potential difference across the battery does not depend on the current.
B
A parallel-plate capacitor is connected in series with a battery and a 30Ω30Ω resistor, as shown above. The capacitor consists of two circular metal plates with radius 1.0cm1.0cm that are separated only by a circular piece of paper with the same radius as the plates. When the capacitor is fully charged, each plate has an excess charge of magnitude 9.0×10−11C9.0×10−11C . The capacitor is replaced by a new capacitor made from two circular metal plates with radius 2.0cm2.0cm that are now separated by two circular pieces of paper with the same radius as the plates. What is the magnitude of the charge on each plate of the new capacitor after it is fully charged? A 36.0×10−11 C36.0×10−11 C B 18.0×10−11 C18.0×10−11 C C 9.0×10−11 C9.0×10−11 C D 4.5×10−11 C
B
The figure above shows a 10 V battery connected in a circuit with two resistors, a parallel-plate capacitor of capacitance C, and three ammeters. The circuit has been connected for a long time. Assume the capacitance C of the capacitor is known. The gap between the capacitor's plates is now filled with an unknown insulating material, and the circuit is again left connected for a long time. Measuring which of the following provides enough information to determine the unknown material's dielectric constant k ? A The potential difference across the capacitor and the current in each branch of the circuit B The potential difference across the capacitor and the charge on one of its plates C The potential difference across the capacitor and the charge on the dielectric material D The separation between the capacitor plates and the area of the plates
B
The figure above shows a region containing a magnetic field of magnitude B� directed into the page. A small loop of wire with a resistance R� is initially at rest in the plane of the page. The loop is partially in the field, enclosing an area A� of the field. While the loop is at rest in the position shown, the magnitude of the magnetic field is gradually increased by an amount ΔBΔ� over a time ΔtΔ�. If an amount of charge Q� passes through point P� while the field is changing, what is ΔBΔ� ? A QR�� B QR/A��/� C QR Δt/A�� Δ�/� D QR/A Δt
B
Wire12345Current (A)0.51.02.02.53.0 A student was given five wires of the same length and diameter. The student connected the wires to the same battery one by one and measured the current through each wire. The table above shows the data collected. Which of the following can be concluded from the data? A The wires are ohmic. B The wires are made of different materials. C The resistance of the wires depends on their size and shape. D The battery has internal resistance.
B
An object with charge -q is in motion near a wire that has a current I to the right. At the instant shown in the figure above, the object is traveling to the right with speed v. Both the wire and the motion of the object are in the plane of the page. Which of the following statements is true about the force on the object due to the current I at the instant shown? A The force is directed toward the top of the page. B The force is directed toward the bottom of the page. C The force is directed toward the right. D There is no force on the object due to the current.
B The force is directed toward the bottom of the page.
A square loop is located in a region containing a magnetic field of magnitude B. The following figures show five possible directions of the magnetic field relative to the loop. For which of the directions is the magnetic flux through the loop greatest?
B straight through the middle (perpendicular to the page)
A capacitor and three resistors are wired in a circuit with a switch S�, as shown above. What is the current through the 3Ω3Ω resistor a long time after the switch has been closed? A 0A0A B 1.3A1.3A C 2.0A2.0A D 2.7A
C
A capacitor with capacitance C0 has a charge Q0. It is then connected in a circuit with a switch and an initially uncharged capacitor with capacitance C0 / 3 , as shown in the figure above. What are the final charges on the capacitors a long time after the switch is closed? (Charge on C0; Charge on C0/3) A Charge on C0Charge on C0 / 3Q0/2Q0/2 B Charge on C0Charge on C0 / 3Q0/32Q0/3 C Charge on C0Charge on C0 / 33Q0/4Q0/4 D Charge on C0Charge on C0 / 32Q0/3Q0/3
C
A circular wire loop is placed near a long, straight, current-carrying wire in which the current is either increasing or decreasing. In which of the following situations is the induced current in the loop counterclockwise? A increasing to the right B increasing up C decreasing to the left D decreasing up E decreasing to the let
C
An air-filled parallel-plate capacitor of capacitance C is connected to a battery and charged to a voltage V. The capacitor is then disconnected from the battery. If the distance between the capacitor plates is halved while the charge on the capacitor remains the same, which of the following is true? A Neither C nor V will change. B Both C and V will be halved. C C will be doubled and V will be halved. D C will be halved and V will be doubled. E Both C and V will be doubled.
C
In the circuit represented above, resistors R1 and R2, capacitor C, and open switch S are connected to a battery. The circuit reaches equilibrium. The switch is then closed, and the circuit is allowed to come to a new equilibrium. Which of the following is a true statement about the charge qf stored on the capacitor after the switch is closed compared with the charge qi stored on the capacitor before the switch is closed? A qf > qi B qf = qi C qf < qi D The relationship between the charges cannot be determined unless the resistances of the resistors are known.
C
In the circuit shown above, R� is a variable resistor. What resistance must R� have so that the voltage across the 1000Ω1000Ω resistor is 5.0 V5.0 V? A 400Ω400Ω B 500Ω500Ω C 1000Ω1000Ω D 5000Ω
C
Refer to the following material to answer the group of questions. The circuit shown above contains four identical lightbulbs with constant resistance, a capacitor C, which is initially uncharged, and a switch S. The switch is initially open. After the switch has been closed a long time, how does the brightness of bulb 4 compare with its brightness before the switch was closed? A Bulb 4 is much dimmer and is only barely lit. B Bulb 4 is slightly dimmer. C Bulb 4 is the same brightness. D Bulb 4 is slightly brighter.
C
The circuit shown above contains four identical lightbulbs with constant resistance, a capacitor C, which is initially uncharged, and a switch S. The switch is initially open. Which of the following correctly ranks the potential differences ∆V1, ∆V2, ∆V3, and ∆V4 across the bulbs while the switch is open? A ∆V1 = ∆V2 = ∆V3 = ∆V4 B ∆V1 > ∆V2 = ∆V3 = ∆V4 C ∆V1 > ∆V2 > ∆V3 = ∆V4 D ∆V1 > ∆V2 > ∆V3 > ∆V4
C
The figure above shows Resistor RR and an initially uncharged capacitor connected in a circuit with a switch and a battery. A long time after the switch is closed, the potential differences across the battery, the resistor, and the capacitor are constant. Which of the following correctly indicates whether the potential differences are zero or nonzero? A The potential difference across the battery is zero, the potential difference across the resistor is nonzero, and the potential difference across the capacitor is nonzero. B The potential difference across the battery is nonzero, the potential difference across the resistor is zero, and the potential difference across the capacitor is zero. C The potential difference across the battery is nonzero, the potential difference across the resistor is zero, and the potential difference across the capacitor is nonzero. D The potential difference across the battery is nonzero, the potential difference across the resistor is nonzero, and the potential difference across the capacitor is zero.
C
The figure above shows Resistor RR and an initially uncharged capacitor connected in a circuit with a switch and a battery. The switch is open and the capacitor is uncharged. A second resistor is added to the circuit, connected between X� and Y� as shown above. How does the potential difference across Resistor RR immediately after the switch is closed compare to that in the original circuit, immediately after the switch is closed? A The potential difference is greater with the new resistor. B The potential difference is less with the new resistor. C The potential difference is the same with the new resistor. D The potential differences cannot be compared without knowing the relative values of the resistances.
C
The figure above shows a circuit containing four resistors, a battery, and two ammeters. The current in ammeter A1 is 1.0 A, and the current in ammeter A2 is 0.6 A. The two resistors labeled R are identical. What are the currents in R2 and in each of the two resistors labeled R? (R2; each R) A R2Each R1.6A0.3A B R2Each R1.6A0.6A C R2Each R0.4A0.3A D R2Each R0.4A0.6A
C
A 20 kΩ resistor is connected in series with an initially uncharged 100 μF capacitor and a 5 V battery. What is the charge on the capacitor when the circuit has reached steady state? A 5 × 104 C B 2.5 × 10-1 C C 2.5 × 10-4 C D 5 × 10-4 C
D
A battery with emf 6.0 V and an internal resistance r is connected to a resistor of resistance R, as shown in Figure 1 above. The current in the circuit is 2.0 A. When an identical battery is added to the circuit in series, as shown in Figure 2, the current in the circuit is 3.0 A. Which of the following statements about the resistances in the circuit is true? A r is very small compared to R. B r is very large compared to R. C r is equal to R. D r and R are comparable in magnitude, but they are not equal.
D
A circular loop of wire is placed in a magnetic field of magnitude B� directed out of the page, as shown. The magnitude of the magnetic field is decreased to zero at a steady rate over a period of time. Which of the following correctly describes the current in the wire while the field is changing? A Momentarily clockwise, then zero for the rest of the time B Momentarily counterclockwise, then zero for the rest of the time C Clockwise the entire time D Counterclockwise the entire time
D
Four horizontal wires are arranged on vertical wooden poles, as shown in the figure above. The wires are equally spaced and have equal currents I in the directions indicated in the figure. The dots represent four charged dust particles moving in the plane of the wires. The sign of the charge on each particle and its direction of motion at a particular instant are shown. Which of the dust particles has a magnetic force exerted on it in the downward direction at this instant? A A B B C C D D
D
In the circuit represented above, the current in the 1 Ω resistor is 4 A. What is terminal voltage V of the battery? A 6 V B 12 V C 18 V D 19 V E 30 V
D
The figure above represents a section of a circuit containing three resistors, X, Y, and Z, of different sizes but made of the same material. Which of the following correctly ranks the current in the resistors? A IZ > IX > IY B IZ = IX > IY C IY = IX = IZ D IY > IX > IZ
D
The figure above shows a metal bar that is supported by two sections of a fixed, conducting U-shaped horizontal rail. The rod and rail are located in a region of magnetic field B directed into the page. The bar is moving to the right at a constant speed. Which of the following is true of the horizontal forces acting on the bar? A There are no forces. B There is only a magnetic force. C There is only an external applied force. D There is both a magnetic force and an external applied force. E Nothing can be said about the forces without knowing the magnitude of the magnetic field.
D
The figure above shows a region containing a magnetic field of magnitude B� directed into the page. A small loop of wire with a resistance R� is initially at rest in the plane of the page. The loop is partially in the field, enclosing an area A� of the field. After a time ΔtΔ� the magnetic field is kept constant. To induce a counterclockwise current in the loop while the field is constant, in what direction should the loop be moved? A Into the page B Out of the page C To the right D To the left
D
Two long, straight wires are perpendicular to the page and carry currents with equal magnitude into the page, as shown above. Points a�, b�, c�, and d� are a distance D� on either side of the axes of the wires. Which of the following correctly ranks the magnitude of the magnetic field B� at these points? A Ba>Bb>Bc>Bd��>��>��>�� B Ba>Bc>Bb>Bd��>��>��>�� C (Ba=Bc)>(Bb=Bd)(��=��)>(��=��) D (Ba=Bd)>(Bb=Bc)
D
What are the value and the direction of the current through the 5Ω5Ω resistor in the circuit shown above? A 1.0A1.0A toward the top of the page B 1.0A1.0A toward the bottom of the page C 2.0A2.0A toward the top of the page D 2.0A2.0A toward the bottom of the page
D
Two long, parallel, straight wires in the plane of the page each carry a current I to the right, as shown above. Points P1 and P2 are in the plane of the page, with P1 being midway between the wires. Which of the following is true of the net magnetic field at the two points that result from the two currents? A Point P1Point P2Directed out of pageDirected into pag B Point P1Point P2Directed out of pageDirected out of page C Point P1Point P2Has magnitude zeroDirected into page D Point P1Point P2Has magnitude zeroDirected out of page E Point P1Point P2Directed into pageDirected into page
D Point P1Point P2Has magnitude zeroDirected out of page
The figure above shows a long, straight wire that has a steady current I in the +y-direction. A small object with charge +q hangs from a thread near the wire. A student wants to investigate the magnetic force on the object due to the current but is not able to observe or measure changes in the tension in the string. Of the following actions that the student can take, which will allow the student to observe a reaction of the object due to the magnetic force on it? A Holding the object motionless B Moving the object in a circle that is centered on the wire and in the x-z plane C Moving the object in the -x-direction D Moving the object in the +y-direction
D Moving the object in the +y-direction
A particle of charge +Q moving with speed vo enters a region of constant magnetic field B directed into the page, as shown above. The initial direction and magnitude of the acceleration of the particle as it enters the magnetic field is toward the A bottom of the page and proportional to B B bottom of the page and proportional to vo C top of the page and inversely proportional to vo D top of the page and inversely proportional to B E top of the page and proportional to both B and vo
E
Charges Q of equal magnitude and opposite sign are on the plates of an isolated parallel-plate capacitor of capacitance C. The voltage between the plates is V, and the energy stored in the capacitor is U. If Q is doubled and C is not changed, how are V and U affected? A VUHalved U Halved B VUHalved U Quartered C VUNot changed U Not changed D VUDoubled U Doubled E VUDoubled UQuadrupled
E
The figure above shows a small compass C that is equidistant from the poles of two identical bar magnets. Which of the following best represents the direction that the needle of the compass will point? Magnet faces what way?
South of compass faces north pole of magnet B
Each of the figures below shows the path of a charged particle moving in the plane of the page in a magnetic field that is perpendicular to the page. If the mass, speed, and charge of the particles are the same, in which case does the field have the greatest magnitude? What would the proton look like
circular path
