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Transcript
Forces and Fields Review Use the following information to answer the next question. A student places a positively charged sphere near a metal rod. Both are on insulated stands and the rod is grounded. 1. The distribution of charge on the rod is A. positive at end X and electrons move off the rod into the ground B. negative at end X and electrons move off the rod into the ground C. positive at end X and electrons move onto the rod from the ground D. negative at end X and electrons move onto the rod from the ground Use the following information to answer the next question. Electrostatic Forces A soap bubble rests on a loop of copper wire. After the wire is touched with negatively charged rod S, the bubble is freed and suspended electrostatically above rod T. 2. The bubble is suspended because A. B. C. D. rod T is positively charged and repels the positive charges on the bubble the bubble induces a positive charge on rod T and is held up by repulsion rod T is negatively charged and repels the negative charges on the bubble the bubble induces a negative charge on rod T and is held up by repulsion -1- 3. A conducting sphere X that has an initial charge of 2.0 ×10–8 C and an identical conducting sphere Y that has an initial charge of –3.0 × 10–8 C are touched together. After they are separated, the charge on sphere X is A. B. C. D. –5.0 × 10–9 C –1.0 × 10–8 C –2.5 × 10–8 C –5.0 × 10–8 C Use the following information to answer the next question. Two identically charged objects are placed near a point, P, as shown below. 4. Which of the following free-body diagrams, drawn to scale, illustrates the electrostatic forces acting on a positive test charge placed at point P? A. B. C. D. -2- Use the following information to answer the next three questions. A student has three identical spheres, K, L, and M, on insulated stands equally spaced in a line as shown below. The charges on the spheres are qK = +3x, qL = − 5x, and qM = +2x. 5. The direction of the net electric force on sphere L due to spheres K and M is A. B. C. D. 6. to the left of the page to the right of the page toward the top of the page toward the bottom of the page At point P, above sphere L, the direction of the net electric field is mostly A. B. C. D. to the left of the page to the right of the page toward the top of the page toward the bottom of the page Use the following additional information to answer the next question. The spheres are touched together and separated, without grounding, in the following order. Step I Step II Step III Spheres K and L Spheres K and M Spheres L and M -3- 7. Which of the following rows indicates the final charge present on each sphere? Row Sphere K Sphere L Sphere M A. 0 0 0 B. −x −x +2x C. D. x 2 x 2 −x x 4 x 2 x 4 Use the following information to answer the next question. Charged spheres I, II and III are located as shown below. 8. The net electrostatic force on sphere III that is caused by the charges on spheres I and II is A. B. C. D. 6.99 × 10−4 N, right 1.06 × 10−3 N, right 6.99 N, right 10.6 N, right -4- Use the following information to answer the next two questions. Three charges, q1, q2, and q3, are placed at the vertices of a right angle triangle, as shown below. 9. The magnitude of the net electrostatic force acting on q2 is A. B. C. D. 212 N 263 N 276 N 327 N Numerical Response 10. The angle labelled θ indicates the direction of the net electrostatic force on q2. The value of θ is __________°. (Record your three-digit answer in the numerical-response section on the answer sheet.) 11. The intensity and direction of the electric field produced by an alpha particle at a distance of 5.0 10–11 m from the particle is A. B. C. D. 5.8 1011 N/C, toward the alpha particle 5.8 1011 N/C, away from the alpha particle 1.2 1012 N/C, toward the alpha particle 1.2 1012 N/C, away from the alpha particle -5- Use the following information to answer the next question. Electric Field Lines Near Two Charged Spheres 12. The types of charge present on X and Y are, respectively, A. B. C. D. negative and negative negative and positive positive and negative positive and positive Numerical Response 13. The electric field strength at a distance of 4.00 cm from a 1.20 × 10−5 C point charge, expressed in scientific notation, is a.bc × 10d N/C. The values of a, b, c, and d are _____, _____, _____, and _____. (Record all four digits of your answer in the numerical-response section on the answer sheet) 14. The magnitude of an electric field at a distance x from a point charge Q is 8.3 10–4 N/C. Q If the distance is increased to 3x and the charge is reduced to , then the magnitude of the 4 electric field will be A. B. C. D. 1.9 10–3 N/C 3.7 10–4 N/C 6.9 10–5 N/C 2.3 10–5 N/C -6- Use the following information to answer the next question. Four point charges are arranged as shown. 15. The magnitude of the net electric field at point P due to these four point charges is A. B. C. D. 5.4 104 N/C 4.5 104 N/C 2.7 104 N/C 0.0 N/C Use the following information to answer the next question. Two point charges of equal magnitude, +Q and –Q, are each placed at an equal distance, x, from point P, as shown below. 16. The direction of the resultant electric field at point P is A. B. C. -7- D. 17. When a charged particle accelerates (increases its speed) in an electric field, there is a decrease in its A. B. C. D. mass charge kinetic energy potential energy Use the following information to answer the next three questions. Cathode-ray tubes (CRTs) are used for television and computer screens. They are set up as shown below. Electrons are “boiled off” the surface of the cathode and are accelerated toward the anode. The cathode is 4.5 cm from the anode. A potential difference of 2.5 103 V exists between the cathode and the anode. The electrons are deflected both side to side and up and down by pairs of magnetic deflection coils mounted on the neck of the tube. 18. An electron hits the screen at a speed of A. B. C. D. 1.0 107 m/s 1.5 107 m/s 3.0 107 m/s 8.8 1014 m/s -8- Use the following additional information to answer the next question. An electron is travelling perpendicular to the magnetic deflection coils, into the page, as shown below. 19. The coils that can produce a deflection toward the top of the screen are numbered A. B. C. D. 20. 1 and 3 2 and 4 1 and 2 3 and 4 An electron accelerates from rest across the gap between charged parallel plates and reaches a final speed of v. If the potential difference across the plates is tripled, the final speed of an electron accelerating from rest across the gap will be A. 1 v 3 B. 1 v 3 C. 3v D. 9 v -9- Use the following information to answer the next question. Magnetic Fields Around Two Bar Magnets 21. Given the magnetic fields illustrated above, the magnets will repel in diagrams A. B. C. D. I and II only I and IV only II and III only II and IV only - 10 - Use the following information to answer the next question. Moving electrons can be deflected by electric fields, gravitational fields, and magnetic fields. One electron is allowed to enter each type of field, as shown below. ● Represents field out of surface × 22. If the electron is deflected downward in each field, then field 1, field 2, and field 3 are, respectively, A. B. C. D. 23. Represents field into surface electric, magnetic, and gravitational gravitational, magnetic, and electric magnetic, gravitational, and electric magnetic, electric, and gravitational Which of the following diagrams best illustrates the magnetic field near a wire that carries an electron current out of the plane of the paper? A. B. C. - 11 - D. 24. When two parallel conducting wires repel each other, the currents in the wires are A. B. C. D. oppositely charged oscillating in phase in the same direction in opposite directions Use the following information to answer the next question. Electrons can produce gravitational, electric, and magnetic fields as a result of the following properties. 1 2 3 Charge Mass Speed Numerical Response 25. Match electron properties as listed above with the field that they produce as given below. You may use a number more than once. There is more than one correct answer. Property: _________ Field: Gravitational Field _________ _________ and __________ Constant Magnetic Electric Field Field (Record all four digits of your answer in the numerical-response section on the answer sheet) 26. The north pole of the solenoid shown to the right is at position A. B. C. D. I II III IV - 12 - 27. The diagrams below show the direction of a magnetic field relative to a set of coordinate axes. A negatively charged particle travels across the page in the positive x direction. The magnetic configuration that will cause the particle to bend in the positive z direction is A. C. B. D. Use the following information to answer the next question. Cross-Section of a Wire Suspended in a Magnetic Field A wire is placed between two permanent magnets. As shown in the diagram, it is positioned so that it is perpendicular to the magnetic field and to the page. The mass of the wire is 0.850 g. The length of the wire perpendicular in the magnetic field is 1.30 cm. Numerical Response 28. When a current of 1.00 A is passing through the wire, there is sufficient magnetic force to keep the wire supported against gravity. The magnitude of the magnetic field, expressed in scientific notation, is a.bc × 10−d T. The values of a, b, c, and d are _____, _____, _____, and _____. (Record all four digits of your answer in the numerical-response section on the answer sheet) - 13 - Use the following information to answer the next two questions. Earth’s Magnetic Field The solar wind consists of particles emitted by the Sun. Some of these particles are charged; therefore, when they enter Earth’s magnetic field, they experience a magnetic force. A stream of charged particles travelling with a speed of 8.00 × 105 m/s encounters Earth’s magnetic field, as shown below, at an altitude where the field has a magnitude of 1.10 × 10–7 T. 29. The protons in the solar wind experience a magnetic force A. B. C. D. into the plane of the page out of the plane of the page in the direction the solar wind is travelling opposite to the direction the solar wind is travelling Numerical Response 30. Assume that the velocity of the solar wind particles is perpendicular to the magnetic field. The radius of the circular path that protons in a solar wind follow, expressed in scientific notation, is a.bc × 10d m. The values of a, b, c, and d are _____, _____, _____, and _____. (Record all four digits of your answer in the numerical-response section on the answer sheet) 31. A proton and an alpha particle have identical circular orbits in a magnetic field. The proton has a speed of 4.4 105 m/s. The speed of the alpha particle is A. B. C. D. 1.1 105 m/s 2.2 105 m/s 4.4 105 m/s 8.8 105 m/s - 14 - Use the following information to answer the next question. The diagram below shows an experimental design used to investigate the effect of a magnetic field on a vertical current-carrying conductor. The aluminum rod is able to swing freely. 32. When the switch is closed, a current in the circuit causes the bottom end of the aluminum rod to swing A. B. C. D. toward the retort stand away from the retort stand toward the south pole of the magnet toward the north pole of the magnet - 15 - Use the following information to answer the next question. Almost all electric guitars use devices called electromagnetic pickups. A guitar string is composed of metal that becomes magnetized by a permanent magnet found below the string. A coil of wire surrounds the permanent magnet. 33. When the string is plucked, a small current is produced in the coil of wire because A. B. C. D. there is a charge buildup on the string a potential difference is produced in the string there is a current in the string that can be amplified the string behaves as a magnet moving toward and away from the coil Unit B: Forces and Fields – Answers 1. D 13. 6747 25. 2113 or 2131 2. C 14. D 26. A 3. A 15. D 27. B 4. C 16. C 28. 6411 5. A 17. D 29. B 6. D 18. C 30. 7594 7. D 19. B 31. B 8. C 20. C 32. B 9. C 21. D 33. D 10. 78.0 22. A 11. D 23. D 12. A 24. D - 16 -