B) 1.12 x 10777 C) 5.6 x 10-78 D) 28 x 1078 3. Two equally positive charges are r distance apart. If the amount of charge on A is doubled and the distance between the charges is doubled, what is the ratio of new electric force to old electric force? A) 1/4 B) 1/2 C) 2 D) 4 4. The amount of work required to move a charge in an electric field depends: A) only on the change in potential and not the path traveled. B) on both the change in potential and the path traveled. C) only on the path traveled and not the change in potential. D) on neither the path traveled nor the change in potential. 5. Which of the following pairs of electric forces form an action-reaction pair? I. Two positive charges, of different masses, placed at a distance d apart. II. Two negative charges, of equal masses, placed at a distance d apart. III. One positive charge and one negative charge, of equal masses, placed at a distance d apart. A) Tand II only B) II and III only C) IIonly D) I, IIand III 6. A hollow metal sphere of radius 0.5 m has a net charge of 2.0 x 10- C. A solid metal sphere of radius 0.5 m has a net charge of 4.0 x 10 C. The centers of the spheres are placed a distance 2 m apart and equilibrium is established. Compared to the electric field at the center of the hollow sphere, the electric field at the center of the solid sphere is: A) twice the magnitude. B) four times the magnitude. C) half the magnitude. D) equal in magnitude. 7. Starting from rest, a sphere of mass 2 kg and charge 0.1 C slides across a frictionless horizontal plane through a potential difference of 220 V. Determine the instantaneous velocity of the sphere the moment it has rolled through this potential. A) 4.7 m/s B) 5.1m/s C) 5.5m/s D) 6.1 m/s CHAPTER 9 PRACTICE PASSAGE In the Bohr model of the atom, electrons circle the point-like nucleus similar to the way planets orbit the Sun. Imagining that the atomic model is confined to motion in one plane, the orbit of the electrons can be drawn as circles with the nucleus in the center. The atomic radius of an atom is defined as the length from the nucleus to the outermost electron and is generally within the tens to hundreds of picometers. The atomic radii of common atoms are as follows: hydrogen = 40 pm, helium = 30 pm, carbon = 80 pm. In the periodic table, atomic radius tends to increase as you go down each column of the table and decrease as you move from left to right across a period. Current scientific thought suggests that the Bohr model is an oversimplification of atomic structure. Quantum mechanics states that the exact position of an electron at a given point in time cannot be known. Only the probability of electron existence in a region of space is known. However, the Bohr model of the atom wonderfully captures another aspect of quantum mechanics: the quantization of energy. The electrons can only have very specific energy values and the distinct orbitals are a very good visual representation of this. Electrons can only move from one energy level to another if there is the exact energy configuration. When dropping from a higher energy to a lower energy, photons with the exact energy difference are emitted, and electrons can only move to a higher energy level if they absorb a photon of the exact energy difference. 1. What is the magnitude of the electric force a hydrogen nucleus exerts on its only orbiting electron in the Bohr model? A) 107N B) 10N C) 107N D) 108N 2. What is the electric potential a millimeter away from a carbon atom nucleus? A) 1.4 x 10V B) 8.6 x 10V C) 14 x 106V D) 8.6 x 103V