TAKE HOME EXAM III
NAME: ______
1. Main difference between gravitational and electric forces is that electric forces a) A Attract. b) Repel or attract c) Obey the inverse square law. d) Act over shorter distance e) Are weaker
2. Electric potential, measured in volts, is the ratio of electric energy to amount of electric a) current b) resistance c) Charge d) voltage
3. When two lamps are connected in series to a battery, the electrical resistance that the battery senses is a) More than resistance of either lamp b) Less than resistance of either lamp c) None of these
4. A 100-Watt lamp glows brighter than a 25-Watt lamp. The electrical resistance of the 100-Watt lamp must be a) Less b) Greater c) The same
5. Two lamps, one with thick filament and one with thin filament, are connected in parallel to a battery. The voltage is greatest across the lamp with the a) Thick filament b) Thin filament c) Both voltages are the same.
6. Compare to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry, a) More current b) Less current c) The same current
7. The source of magnetism is a) Tiny piece of iron b) Tiny domains of aligned atoms c) Ferromagnetic materials d) Moving electric charges
8. If a steady magnetic field exerts a force on a moving charge, the force is directed a) Opposite the motion b) In the direction of motion c) At right angles to the direction of motion 9. Voltage can be induced in a wire by a) Moving the wire near a magnet b) Moving magnet near the wire c) Changing the current in a nearby wire d) All of these e) None of these.
10. Which pole of a compass needle points to a south pole of a magnet? a) north pole b) south pole c) both of these
11. Compared to the amount of electric current in the filament of a lamp, the amount of current in the conducting wire is a) less b) more c) the same
12. An electric heater is rated at 300 W when used in a 10-V circuit. The safety fuse in the circuit can handle 15A of current How many heaters can be safely operated in the circuit? a) 12 b) 3 c) 4 d) 5
13. A heater uses 20 A when used in a 110 V line. If the electric power costs 10 cents per kilowatt hour, the cost of running the heater for 10 hours is a) $0.22 b) $0.55 c) $2.20 d) $5.30
14. Stretch a copper wire so that is thinner and the resistance between its ends a) decreases b) remains unchanged c) increases
15. Electrons are made to flow in a wire when there is a) an unbalance of charges in the wire b) more potential energy at one end of the wire than the other. c) a potential difference across its ends.
16. A proton and electron are placed in an electric field. Which undergoes the greater acceleration? a) electron b) proton c) both accelerate equally d) neither accelerates 17. You can touch a 100,000 volt Van de Graff generator with little harm because although the voltage is high, the relatively small amount of charge means there is a relatively small amount of a) electric field b) energy c) polarization d) conduction
18. Which of these colors of light has photons of greatest energy? a) green b) red c) blue d) yellow
19. Which of these colors of light has photons of lowest energy? a) blue b) green C) yellow D) red
20. When an electron goes from an excited state to the ground state, a) energy is absorbed. b) a photon is absorbed. c) a photon is emitted. d) None of these occur
21. When fast electrons strike a metal target, what are produced? a) radio waves b) gamma rays c) X-rays d) microwaves
22. When an electron in an atom moves from a lower energy level to a higher one, a ______is ______.
a) photon; emitted b) proton; emitted c) photon; absorbed d) proton; absorbed
23 23. How many protons are there in an atom of 11 Na ? a) 12 b) 34 c) 23 d) 11
39 24. How many neutrons are there in an atom of 19 K ? a) 19 b) 20 c) 39 d) 58 56 25. How many electrons are there in an atom of 26 Fe ? a) 26 b) 30 c) 82 d) 56
26. What is the symbol for the element whose atoms have 40 electrons each? a) Ge b) Zr c) Ar d) None of these
27. The mass number (A) of a nuclide is equal to the number of ______in one of its nuclei. a) protons plus neutrons b) protons c) neutrons d) neutrons plus electrons
28. The most important force between a proton and a neutron is the ______force. a) strong nuclear b) quark c) electromagnetic d) gravitational
29. Name the isotope of hydrogen that is radioactive. a) protium b) tritium c) deuterium d) hydronium
30. When an oxygen-19 nucleus undergoes beta decay, the nucleus formed is that of a)] nitrogen-18. b) oxygen-18. c) fluorine-19. d) carbon-14.
226 31. When 88 Ra undergoes alpha decay, the daughter is 222 a) 86 Rn . 230 b) 90Th . 226 c) 89 Ac . 1 d) 1 H .
32. When the number of protons in a nucleus exceeds ______, the nucleus is unstable. a) 65 b) 56 c) 83 d) 103 238 234 33. When 92 U decays to 90Th , a(n) ______is emitted. a) beta particle b) deuteron c) gamma ray d) alpha particle
34. After three half-lives have elapsed, what fraction of the original amount of radionuclide remains? a) 1/3 b) 1/4 c) 1/8 d) None of these
35. Plutonium-239 and uranium-235 undergo fission when bombarded by a) protons. b) neutrons. c) alpha particles. d) electrons.
36. The smallest amount of a fissionable material that will give a self-sustaining chain reaction is called the a) mass defect. b) mass number. c) atomic mass. d) critical mass.
37. To say that electric charge is quantized is to say that the charge on an object a) may occur in an infinite variety of quantities. b) Is a whole number multiple of the charge of one electron? c) Will interact with neighboring electric charges. d) Can be neither created nor destroyed.
38. An electron is pushed into an electric field where it acquires a 1-V electrical potential. If two electrons are pushed the same distance into the same electric field, the electrical potential of the two electrons is a) 0.25 V b) 0. 5 V c) 1 V d) 2 V
39. A wire carrying current is normally charged a) negatively b) positively c) not at all 40. Alternating current is normally produced by a a) battery b) generator c) both of these d) neither of these 41. Touch the 100 volt battery and you are jolted. Touch a 10,000 volt rubber balloon and you feel nothing. Why?
42. You have two electrically neutral metal cylinders that exert strong attractive forces on each other. You have no other metal objects. Can you determine if both of cylinders are magnets, or if one is magnet and the other just a piece of iron? If so, how? If not, why not?
43. Four lightweight balls A, B, C, and D are suspended by threads. Ball A has been touched by a plastic rod that is rubbed with wool. When the balls are brought close together, without touching the following observations are made: . Ball B, C, and D are attracted to ball A . Ball B and D have no effect on each other . Ball B is attracted to ball C. What are the charge states of balls A, B, C, and D? Explain.
44. Metal sphere A has 4 units of negative charge and metal sphere B has 2 units of positive charge. The two spheres are brought into contact. What is the final charge state of each sphere? Explain.