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Unformatted text preview: Solution for Practice Test 3 for Test 1 Solution to Practice Test Problem 3.1(What is Charge?) Problem: What is electric charge? Select the answer below that best describes electric charge Select One of the Following: (a) A powder attached to all matter. (b) An excess or deficiency in electrons. (c-Answer) A feature of all matter, defined by its effects. (d) A fluid that flows through conducting wires. Solution A feature of all matter. Total Points for Problem: 3 Points Solution to Practice Test Problem 3.2(Flux Out of Gaussian Cylinder) Problem: Consider the geometry at the right where a cylindrical Gaussian surface is placed within a uniform electric field with magnitude 75 N C . The radius of the end of the Gaussian surface is . 2m and the height of the cylinder is . 3m . Compute the electric flux OUT of the Gaussian surface that passes through the LEFT end, the RIGHT end, and the curved sides. Select One of the Following: (a-Answer) left =- 9 . 4 N C m 2 , right = 9 . 4 N C m 2 , sides = 0 . (b) left = 9 . 4 N C m 2 , right = 9 . 4 N C m 2 , sides = 0 . (c) left =- 9 . 4 N C m 2 , right = 9 . 4 N C m 2 , sides = 28 N C m 2 . (d) left = 9 . 4 N C m 2 , right =- 9 . 4 N C m 2 , sides = 28 N C m 2 . (e) left = 9 . 4 N C m 2 , right =- 9 . 4 N C m 2 , sides = . A Solution The flux out the left end is left =- EA =- Er 2 =- (75 N C ) (0 . 2m) 2 =- 9 . 4 N C m 2 . The flux is negative because the field lines go in. There is no flux out the sides sides = 0 . The flux out the right has the same magnitude but different sign of the flux out the left, right = EA = 9 . 4 N C m 2 . Total Points for Problem: 3 Points 1 Solution to Practice Test Problem 3.3(Why Zero force in conductor?) Problem: In chapter two, we argued that a short time after a conductor is placed in an external electric field the net electric force felt by the mobile charge inside the conductor becomes zero. What explained this effect physically? Select One of the Following: (a) Mobile charges blocked the field lines. (b-Answer) Charge separated in response to the external field and set up a field that cancelled the external field in the conductors interior. (c) The surface atoms lost electrons to the air to block the field. (d) The atoms in the conductor absorb the electric field. (e) A Gaussian surface enclosing the conductor contained no net charge. Solution Charge separated in response to the external field and set up a field that canceled the external field in the conductors interior. Total Points for Problem: 3 Points Solution to Practice Test Problem 3.4(What charge is in a region?) Problem: A field map is shown to the right, the dashed region contains a distribution of charge. Select one of the following that best describes the distribution of charge....
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