Physics Test Review Electrostatics, Electric Fields and Potential Session: Name:

Transcription

1 Physics Test Review lectrostatics, lectric Fields and Potential Session: Name: Multiple hoice Identify the letter of the choice that best completes the statement or answers the question. 1. Two unlike charges a) polarize each other. b) repel each other. c) must be neutrons. d) attract each other. e) have no effect on each other. 2. oulomb's law says that the force between any two charges depends a) directly on the size of the charges. b) inversely on the square of the distance between the charges. c) both and d) none of the above 3. Two charges are separated by a certain distance. If the magnitude of each charge and the distance are both doubled, the force on each charge is a) the same. b) halved. c) doubled. d) tripled. e) quadrupled. 4. positive ion has a) more electrons than protons. b) more protons than electrons. c) a +1 charge always. d) one proton. e) one neutron. 5. onservation of charge means that a) the total amount of charge in the universe is constant. b) no experimenter has ever seen a single charge destroyed by itself. c) electrons by themselves can be neither created nor destroyed. d) charge can be neither created nor destroyed. e) all of the above 6. The SI unit of charge is the a) volt. d) newton/coulomb. e) newton. 7. Which of the following statement is wrong? a) The net charge of a ion is not zero. b) harge can not be created or destroyed. c) lectric charges are always multiple of a fixed unit charge. d) Thomson s experiment proved that the electric charges are positive. e) Protons are more massive than electrons, however, they have the same amount of charges, just different signs. 8. harge carriers in a metal are electrons rather than protons, because electrons are a) neutral. b) in the center of a nucleus. c) bounded to the atom. d) lighter. 9. In a good insulator, electrons are usually a) not moving at all. b) free to move around after an impurity has been added. c) free to move around. d) tightly bound in place. e) semi-free to move around. 10. conductor differs from an insulator in that a conductor has a) more protons than electrons. b) faster-moving molecules. c) more electrons than protons. d) more electrons than an insulator. 11. Much electronic equipment contains transistors and diodes that are made from semiconductors. Semiconductors a) can be very good insulators. b) can conduct electricity. c) contain helpful impurities. 12. To say that electric charge is conserved means that no case has ever been found where a) the total amount of charge on an object has increased. b) one object has more charge than another object. c) the total charge on an object has changed. d) charge are fractions of 1.6 x difference between electrical forces and gravitational forces is that electrical forces include a) infinite range. b) the inverse square law. c) force at distance. d) repulsive interactions. 14. Objects can be charged by a) contact b) induction. c) friction. 15. The reason a charged balloon will stick to a wall is that a) the rubber of the balloon simply sticks to walls. b) electrons transfer back and forth between the wall and the balloon. c) induced opposite charges in the wall are closer than the like charges. d) the charge is slightly sticky and acts like glue. 16. positively charged rod is brought near a metal can that rests on a wood table. You touch the opposite side of the can momentarily with your finger. The can is then a) negatively charged. 1 Mr. Lin

2 Physics Test Review lectrostatics, lectric Fields and Potential Session: Name: b) positively charged. c) charged the same as it was. d) uncharged When a charged cloud passes overhead, the ground below is charged by a) induction. b) polarization. c) deduction. d) electrification. 18. n electroscope is charged negatively, as shown by foil leaves that stand apart. s a negatively charged rod is brought close to the electroscope, the leaves a) spread farther apart. b) move closer together. c) do not move. d) can not be determined. 19. lectrical polarization occurs when a) an electron is at a different location than a proton. b) charge distribution in a neutral molecule separates. c) the electron and the proton are on different sides of an atom. d) an atom vibrates in a single direction. 20. negatively charged rod touches an irregular metal shape at point and then removed. Where do you expect to have the highest density of negative charges a) b) c) d) e) 21. Which of the following statement is false? a) The semiconductor becomes conductive when doped with impurities. b) In a good conductor, electrons are usually free to move around. c) conductor has more electrons than protons. d) Water is a poor conductor. e) None of the above. 22. The charge distribution in some molecules is permanently separated into positive and negative regions. Such molecules are called a) ionized molecules. b) coulomb molecules. c) induced molecules. d) electric dipoles. e) insulators. 23. positively charged metal ball with charge 3.2 x 10-8 contacts with an identical electrically neutral metal ball. fter a while, separate these two balls, and each one has charge a) 1.6 x b) 3.2 x c) 2.4 x 10-8 d) 1.6 x 10-8 e) 3.2 x Two charged particles held near each other are released. s they move, the acceleration of each increases. Therefore, the particles have a) opposite signs. b) the same sign. c) charges that can not be determined. 25. Two charged particles held close to each other are released. s they move, the force on each particle decreases. Therefore, the particles have a) opposite signs. b) the same sign. c) charges that cannot be determined 26. Two charged particles held close to each other are released. s the particles move, the velocity of each increases. Therefore, the particles have a) the same sign. b) opposite signs. c) charges that cannot be determined charge and a 4- charge attract each other with 10 N of force. How much will a 4- charge and a 8- charge attract each other when placed the same distance apart? a) 5 N b) 10 N c) 20 N d) 30 N e) 40 N 28. Two charges separated a distance of 1.0 meter exert a 2.0-N force on each other. If the charges are pushed to a separation of 1/2 meter, the force on each charge will be a) 1.0 N. b) 4.0 N. c) 6.0 N. d) 8.0 N. e) 18.0 N. 29. Two charges separated by a distance of 1 meter exert a 2-N force on each other. If the magnitude of each charge is doubled, the force on each charge is a) 2 N. b) 4 N. c) 8 N. d) 16 N. 30. The SI unit of electric field is the a) ohm. d) newton/column. e) newton. 31. The direction of electric field lines shows the a) direction of the force on a test positive charge. b) size of the field. c) strength of the field. 32. Van de Graaff generator is a machine that a) generates light. b) works like a motor. c) generates electricity. d) builds up high voltages. 2 Mr. Lin

3 Physics Test Review lectrostatics, lectric Fields and Potential Session: Name: 33. Suppose a hollow metal sphere has a large negative charge on it. The electric field strength inside the sphere is a) large and positive. b) weak and negative. c) weak and positive. d) zero. e) large and negative. 34. The SI unit of electric potential is the a) ohm. d) newton/column. e) volt. 35. lectric potential is defined as a) electrical potential energy. b) electrical potential energy of a charge multiplied by the quantity of the charge. c) electrical potential energy of a charge divided by the quantity of the charge. d) gravitational potential. e) voltage. 36. lectrical potential energy is the energy a charged object has because of its a) momentum. b) mass. c) motion. d) location. e) volume. 37. small, positively charged object near a negatively charged sphere is moved closer to the sphere. The electrical potential energy of the small object a) stays the same. b) decreases. c) increases. d) can not be determined. 38. When an electron is brought near a negatively charged sphere, its potential energy increases. The reason this happens is that a) two like charges go from a position far apart to a position close together. b) negative charges repel each other. c) work was done to bring the charges together. d) none of the above 39. woman's hair stands out when she is in contact with a charged Van de Graaff generator. The reason her hair stands out is because a) friction. b) hair strands are at a high voltage. c) she is in a strong electric field. d) like charges repel. e) hair is a good conductor. 40. The electric field around an isolated electron has a certain strength 1 cm from the electron. The electric field strength 2 cm from the electron is a) half as much. b) one fourth. c) twice as much. d) four times as much. 41. lectrical potential energy per charge is electric a) field. b) force. c) power. d) potential. e) work. 42. lectric field lines between two oppositely charged parallel metal plates will be a) straight lines, randomly spaced. b) straight lines, evenly spaced. c) curved lines grouped together in small bunches. d) curved lines, evenly spaced. e) curved lines, randomly spaced. 43. The electric field in a certain region of space is 15 N/. What is the force on a 2- charge placed in that region? a) 15 N b) 2 N c) 30 N d) 4 N e) 60 N charge is located near a positively charged sphere so that it has 30 J of electric potential energy. Its electric potential is a) 2 V. b) 5 V. c) 10 V. d) 20 V. e) 250 V. 45. The electrical force on a 3- charge is 30 N. What is the value of the electric field at the location of the charge? a) 2 N/ b) 10 N/ c) 20 N/ d) 30 N/ e) 60 N/ nswer Keys Mr. Lin

4 Physics Test Review lectrostatics, lectric Fields and Potential Session: Name: Word Problem Show all work for the following questions, including the equation and substitution with units. 1. Three charged metal balls,, and are shown in the diagram. all and contacts each other momentarily, and then ball and contacts each other momentarily. What are the charges of ball,, and? +4q +2q -3q 4. If a positive test charge is located between two charged spheres, and. Sphere has a charge of +4q and is located 0.3 meter from the test charge. Sphere has a charge of -2q and is located 0.1 meter from the test charge. If the magnitude of the force on the test charge due to sphere is 5 N, what is the magnitude of the force on the test charge due to sphere? Test harge +4q + -2q 0.3 m 0.1 m [all : +3q, all : 0; all : 0] [22.5 N] 2. etermine the electrical force of attraction between two balloons with separate charges of 3.5 x 10-8 and -2.9 x 10-8 when separated a distance of 0.65 m 5. The hydrogen atom consists of a proton and a single electron at an average separation distance of 5.3 x m. alculate the electrical force between the proton and the electron in a hydrogen atom. [2.16 x 10 5 N] [8.19 x 10 8 N] 3. ach of the two identical hot-air balloons acquires a charge of 4.8 x 10 3 on its surface as it travels through the air. How far apart are the balloons if the electrostatic force between them is 2.4 N? 6. (a) What are the magnitude and direction of the electric field 2.0 m away from a negatively charged particle of 3.2 x 10 2? (b) What are the magnitude and direction of the electric force when an electron is placed 2.0 m away from this particle? (a) [7.19 x 10 7 N/] [Toward the negatively charged particle] [ m] (b) [1.15 x N] [way from the negatively charged particle] 4 Mr. Lin

5 Physics Test Review lectrostatics, lectric Fields and Potential Session: Name: 7. Use Line-of-force representation to draw the electric field and equipotential lines surrounding a pair of unlike charges. 11. If an electron loses 6.0 x J of energy in traveling from the cathode to the screen of a computer monitor, across what potential difference must it travel? [3.75 x 10 9 V] 8. What is the magnitude of the electric field strength when an electron experiences a 3.6 x 10 3 N force? 12. charged droplet of mass 5.87 x kg is hovering motionless between two parallel plates. The parallel plates have a potential difference of V and are 1.00 mm apart. (a) What is the strength of the electric field? (b) What is the charge on the particle? (c) y how many electrons is the particle deficient? [2.25 x N/] 9. fly acquires 8.0 x of positive charge as it flies through the air. What is the magnitude and direction of the electric field at a location 10.0 cm away from the fly? (a) [3.6 x 10 7 N/] (b) [1.6 x ] (c) [1000 electrons] [719.2 N/] [way from the fly] 10. The electron beam in the TV tube is steered across the screen by the electric field between two charged plates. If the electron experiences a force of 6.4 x 10 5 N, how large is the field between the deflection plates? [4.0 x N/] 5 Mr. Lin