Flashcards
physics 250b final mcq
Flashcards do conjunto (60)
- 1At a distance D from a very long (essentially infinite) uniform line of charge, the electric field strength is 1000 N/C. At what distance from the line will field strength be 2000 N/C.D/2
- 2The electric field 1.5 cm from a very small charged object points toward the object with a magnitude of 180,000 N/C. What is the charge on the object?-4.5 nC
- 3Consider the group of three+2.4 C point charges shown in the figure. What is the electric potential energy of this system of charges relative to infinity?4.1 x 10^-6
- 4If the electric field is zero everywhere inside a region of space, the potential must also be zero in that region.False
- 5The graph in the figure shows the variation of the electric potential V (measured in volts) as a function of the radial direction r (measured in meters). For which range or value of r is the magnitude of the electric field the largest?from r=3 to r=4 m
- 6The figure shows two unequal point charges, q and Q, of opposite sign. Charge Q has greater magnitude than charge q. In which of the regions X, Y, Z will there be a point at which the net electric field due to these two charges is zero?only region X
- 7Under electrostatic conditions, the electric field just outside the surface of any charged conductoris always perpendicular to the surface of the conductor.
- 8In the figure, all the charges are point charges and the charge in the middle is Q=-3.1 NC. For what charge q1 will charge q2 be in static equilibrium?12 nC
- 9The figure shows two connected wires that are made of the same material. The current entering the wire on the left is 2.0 A and in that wire the electron drift speed is Y. What is the electron drift speed in the wire on the right side?v_d/4
- 10A charged particle is moving with speed v perpendicular to a uniform magnetic field. A second identical charged particle is moving with speed 2v perpendicular to the same magnetic field. If the trequency of revolution of the first particle is f, the frequency of revolution of the second particle isf
- 11An electron, moving toward the west, enters a uniform magnetic field. Because of this field the electron curves upward. The direction of the magnetic field istowards the north
- 12Two light bulbs, By and By, are connected to a battery having appreciable internal resistance as shown in the figure. What happens to the brightness of bulb By when we close the switch S?the brightness of B1 decreases permanently
- 13In the circuit shown in the figure, four identical resistors labeled A to D are connected to a battery as shown. S1 and S2 are switches. Which of the following actions would result in the GREATEST amount of current through resistor A?closing both switches
- 14An ideal parallel-plate capacitor consists of a set of two parallel plates of area A separated by a very small distance d. When the capacitor plates carry charges +Q and -Q, the capacitor stores energy U_0. If the separation between the plates is doubled, how much electrical energy is stored in the capacitor?U_0
- 15A narrow copper wire of length L and radius b is attached to a wide copper wire of length L and radius 2b, forming one long wire of length 21. This long wire is attached to a battery, and a current is flowing through it. If the electric field in the narrow wire is E, the electric field in the wide wire isE/2
- 16A narrow copper wire of length L and radius b is attached to a wide copper wire of length L and radius 2b, forming one long wire of length 21. This long wire is attached to a battery, and a current is flowing through it. If the electric field in the narrow wire is E, the electric field in the wide wire isE/4
- 17The charge on the square plates of a parallel-plate capacitor is Q. The potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared to the dimensions of the plates. The amount of charge on the plates is now equal to.Q/2
- 18In the figure, a straight wire carries a current I. The wire passes through the center of a toroidal coil. If the current in the wire is quickly reduced to zero, the induced current through the resistor R isfrom b to a
- 19Three point charges of -2.00 μC, +4.00 μC, and +6.00 μC are placed along the x-axis as shown in the figure. What is the electrical potential at point P (relative to infinity) due to these charges? (k = 1/4πε0 = 8.99 × 109 N • m2/C2)+307 kV
- 20The figure shows an arrangement of two - 4.5 nC charges, each separated by 5.0 mm from a proton. If the two negative charges are held fixed at their locations and the proton is given an initial velocity v as shown in the figure, what is the minimum initial speed v that the proton needs to totally escape from the negative charges?1.8 x 10^6 m/s
- 21The figure shows two long wires carrying equal currents I1 and I2 flowing in opposite directions. Which of the arrows labeled A through D correctly represents the direction of the magnetic field due to the wires at a point located at an equal distance d from each wire?B
- 22Which of the following statements about inductors are correct? There may be more than one correct choiceAn inductor always resists any change in the current through it.
- 23A nonconducting sphere contains positive charge distributed uniformly throughout its volume. Which statements about the potential due to this sphere are true? All potentials are measured relative to infinity. (There may be more than one correct choice.)The potential is highest at the center of the sphere.
- 24Two long parallel wires placed side-by-side on a horizontal table carry identical size currents in opposite directions. The wire on your right carries current toward you, and the wire on your left carries current away from you. From your point of view, the magnetic field at the point exactly midway between the two wirespoints downward
- 25A large magnetic flux change through a coil must induce a greater emf in the coil than a small flux change.false.
- 26Three particles travel through a region of space where the magnetic field is out of the page, as shown in the figure. The electric charge of each of the three particles is, respectively,1 is negative, 2 is neutral, 3 is positive
- 27A charge is accelerated from rest through a potential difference V and then enters a uniform magnetic field oriented perpendicular to its path. The field deflects the particle into a circular arc of radius R. If the accelerating potential is tripled to 3V, what will be the radius of the circular arc?sqrt(3) R
- 28A negative charge, if free, will tend to movefrom low potential to high potential
- 29Three resistors having resistances of 4.0 Ω, 6.0 Ω, and 10.0 Ω are connected in parallel. If the combination is connected in series with an ideal 12-V battery and a 2.0-Ω resistor, what is the current through the 10.0-Ω resistor?0.59 A
- 30The three loops of wire shown in the figure are all subject to the same uniform magnetic field that does not vary with time. Loop 1 oscillates back and forth as the bob in a pendulum, loop 2 rotates about a vertical axis, and loop 3 oscillates up and down at the end of a spring. Which loop, or loops, will have an emf induced in them?loop 2 only
- 31The graph in the figure shows the variation of the electric potential V (measured in volts) as a function of the radial direction r (measured in meters). For which range or value of r is the magnitude of the electric field the largest?from r=3 to r=4 m
- 32The figure shows a bar magnet moving vertically upward toward a horizontal coil. The poles of the bar magnets are labeled X and Y. As the bar magnet approaches the coil it induces an electric current in the direction indicated on the figure (counterclockwise as viewed from above). What are the correct polarities of the magnet?X is a south pole, Y is a north pole
- 33A charged particle is moving with speed v perpendicular to a uniform magnetic field. A second identical charged particle is moving with speed 2v perpendicular to the same magnetic field. If the frequency of revolution of the first particle is f, the frequency of revolution of the second particle isf
- 34Thirteen resistors are connected across points A and B as shown in the figure. If all the resistors are accurate to 2 significant figures, what is the equivalent resistance between points A and B?8.0 ohms
- 35In the figure, a bar magnet moves away from the solenoid. The induced current through the resistor R isfrom a to b
- 36An electron is initially moving to the right when it enters a uniform electric field directed upwards. Which trajectory shown below will the electron follow?Trajectory Z
- 37The figure shows four different sets of insulated wires that cross each other at right angles without actually making electrical contact. The magnitude of the current is the same in all the wires, and the directions of current flow are as indicated. For which (if any) configuration will the magnetic field at the center of the square formed by the wires be equal to zero?C
- 38Two point charges of +2.0 μC and -6.0 μC are located on the x-axis at x = -1.0 cm and x = +2.0 cm respectively. Where should a third charge of +3.0-μC be placed on the +x-axis so that the potential at the origin is equal to zero?3.0 cm
- 39In the figure, a straight wire carries a steady current I perpendicular to the plane of the page. A bar is in contact with a pair of circular rails and rotates about the straight wire. The direction of the induced current through the resistor R isThere is no induced current through the resistor
- 40A circular loop of wire lies in the plane of the paper. An increasing magnetic field points out of the paper. What is the direction of the induced current in the loop?clockwise
? - 41A vertical wire carries a current straight down. To the east of this wire, the magnetic field pointsto the south
- 42The figure shows three long, parallel current-carrying wires. The magnitudes of the currents are equal and their directions are indicated in the figure. Which of the arrows drawn near the wire carrying current 1 correctly indicates the direction of the magnetic force acting on that wire?A
- 43A charge of 1.0 × 10-6 μC is located inside a sphere, 1.25 cm from its center. What is the electric flux through the sphere due to this charge?0.11 N • m2/C
- 44The figure shows two unequal point charges, q and Q, of opposite sign. Charge Q has greater magnitude than charge q. In which of the regions X, Y, Z will there be a point at which the net electric field due to these two charges is zero?only region X
- 45A nonuniform electric field is directed along the x-axis at all points in space. This magnitude of the field varies with x, but not with respect to y or z. The axis of a cylindrical surface, 0.80 m long and 0.20 m in diameter, is aligned parallel to the x-axis, as shown in the figure. The electric fields E1 and E2, at the ends of the cylindrical surface, have magnitudes of 6000 N/C and 1000 N/C respectively, and are directed as shown. What is the net electric flux passing through the cylindrical surface?-160 N • m2/C
- 46What is the self-inductance of a solenoid 30.0 cm long having 100 turns of wire and a cross-sectional area of 1.00 × 10-4 m2? (μ0 = 4π × 10-7 T • m/A)4.19 µH
- 47A capacitor is charging in a simple RC circuit with a dc battery. Which one of the following statements about this capacitor is accurate?There is a magnetic field between the capacitor plates, even though no charge travels between them,
because the electric flux between the plates is changing. - 48At what rate would the current in a 100-mH inductor have to change to induce an emf of 1000 V in the inductor?10,000 A/s
- 49If the electric potential at a point in space is zero, then the electric field at that point must also be zero.False
- 50Two point charges Q1 and Q2 of equal magnitudes and opposite signs are positioned as shown in the figure. Which of the arrows best represents the net electric field at point P due to these two charges?A
- 51If the electric flux through a closed surface is zero, the electric field at points on that surface must be zero.false
- 52An electron moving in the direction of the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, the direction of the magnetic field in this region points in the direction of the- z axis
- 53If the electric field is zero everywhere inside a region of space, the potential must also be zero in that region.False
- 54Two large, flat, horizontally oriented plates are parallel to each other, a distance d apart. Halfway between the two plates the electric field has magnitude E. If the separation of the plates is reduced to d/2 what is the magnitude of the electric field halfway between the plates?E
- 55When the electric field is zero at a point, the potential must also be zero there.false.
- 56Suppose you have two-point charges of opposite sign. As you move them farther and farther apart, the potential energy of this system relative to infinityincreases
- 57Three equal negative point charges are placed at three of the corners of a square of side d as shown in the figure. Which of the arrows represents the direction of the net electric field at the center of the square?C
- 58The figure shows three identical lightbulbs connected to a battery having a constant voltage across its terminals. What happens to the brightness of lightbulb 1 when the switch S is closed?the brightness increases permanently
- 59A wire of resistivity ρ must be replaced in a circuit by a wire of the same material but 4 times as long. If, however, the resistance of the new wire is to be the same as the resistance of the original wire, the diameter of the new wire must be2 times the diameter of the original wire
- 60A light bulb is connected in the circuit shown in the figure with the switch S open and the capacitor uncharged. The battery has no appreciable internal resistance. Which one of the following graphs best describes the brightness B of the bulb as a function of time t after closing the switch?graph 2
increases, then plateaus
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- FlashCards sobre physics 250b final mcq , criado por Star Sarode em 07-12-2022.
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