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Unformatted text preview: Solution for Practice Test 2 for Test 1 Solution to Practice Test Problem 2.1(Define Electric Charge) Problem: What is electric charge? Select One of the following which best defines electric charge. Select One of the Following: (a) Something that cannot be created or destroyed. (bAnswer) A feature of every object in the universe, defined by its effects. (c) An excess or deficit of electrons. Solution A feature of every object in the universe, defined by its effects. Total Points for Problem: 3 Points Solution to Practice Test Problem 2.2(Rotation of a Dipole in the Field of a Second Dipole) Problem: The figure to the right shows two electric dipoles. Dipole A is fixed in place and dipole B is allowed to move freely. Select the choice that best describes the initial motion of the dipole. Select One of the Following: (a) No motion, the dipole is at equilibrium. (b) Rotate clockwise, move ˆ y direction. (c) Rotate clockwise, move +ˆ y direction. (dAnswer) Rotate counterclockwise, move +ˆ y direc tion. (e) Rotate counterclockwise, move ˆ y direction. y x Fixed p A p B Solution 1 The field of the dipole A and forces on each end of the dipole B are drawn to the right. The net force is mostly in the +ˆ y direction. This force causes the dipole to move in the +ˆ y direction. The dipole will also rotate counterclockwise. y x Fixed + p A p B Total Points for Problem: 3 Points Solution to Practice Test Problem 2.3(What Laws Required to Calculate any Electric Field) Problem: Any static electric field can be calculated by cutting the system up into small bits, calculating the field of each piece, and adding the fields vectorially. What two physics laws do you use in this process? Select One of the Following: (a) Coulomb’s Law and the Law of Quantization of Charge (b) Gauss’s Law and the Law of Conservation of Charge (c) Gauss’s Law and Coulomb’s Law (d) Gauss’s Law and the Law of Linear Superposition (eAnswer) Coulomb’s Law and the Law of Linear Superposition Solution Coulomb’s Law and the Law of Linear Superposition Total Points for Problem: 3 Points Solution to Practice Test Problem 2.4(Sign of Charges Required to Float Pith Ball) 2 Problem: A positively charged pith ball floats between two infi nite charged planes. Gravity acts in the ˆ y direction. The charge densities on the two planes have the same magnitude  σ b  =  σ t  , but may have different signs. Select the combination of signs that will cause the pith ball to float if the charge density is large enough. Select One of the Following: (a) σ b > and σ t > . (bAnswer) σ b > and σ t < . (c) σ b < and σ t < . (d) σ b < and σ t > . (e) No combination will float the pith ball....
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This note was uploaded on 05/04/2008 for the course PHYS 2074 taught by Professor Stewart during the Spring '08 term at Arkansas.
 Spring '08
 Stewart
 Physics, Charge

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