quiz1-solutions

quiz1-solutions - and the vector to the charge location,...

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1 The solutions are in order of the questions for version 1. (1). Correct answer A The electric Felds in C and D are zero, In A, B, the x-component cancels and we just have a y-component. In A the y-component resulting from each of the charges points down and hence these all add; in B, some point down and some point up, partially canceling the Feld strength. (2). Correct answer is B The force Q E must equal ma; hence Q= (.275)(13)/5 = .72 C (3). Correct answer is B The Feld due to a large plate in independent of the distance from the plate. Hence the Feld contributions from the negative and positive charges exactly cancel, giving zero. (4). Correct answer is D Plugging in the numbers, the electric force if (9 × 10 9 )(20 × 10 - 6 ) 2 (150) 2 1 . 5 × 10 - 4 The gravitational contribution is almost completely negligible (5). Correct answer is B There is no y-component from the Q = 1 μC charge; using the fact that the distance is 2m and that the y-component is proportional to sine of the angle between the x-axis
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Unformatted text preview: and the vector to the charge location, the other charge gives a negative y-component with magnitude (9 10 9 )(2 10-6 ) (2) 2 1 . 6 2 3600 (6). Correct answer is D The force is just (9 10 9 )(2 10-6 )(1-6 ) (1 . 6) 2 . 007 (7). Correct answer is E This is the Feld pattern for an electric dipole; the two charges are equal and have opposite signs and there are Feld lines (and hence non-zero Feld values) at the two points. Hence the answer is E. 2 (8). Correct answer is A By Gauss law, there must be a total of -300 nC spread around the inner surface; the charge density is then this charge, divided by the surface area of 4 ( . 8) 2 . (9). Correct answer is D The Feld is always zero inside a conductor (10). Correct answer is C The total charge interior to r= 1.5 is -200nC. The Feld is therefore (9 10 9 )( 200 10-9 ) (1 . 5) 2 800...
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This note was uploaded on 10/16/2011 for the course PHYS 1B taught by Professor Briankeating during the Winter '07 term at UCSD.

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quiz1-solutions - and the vector to the charge location,...

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