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Unformatted text preview: Solution for Homework 3 Beginning Electric Fields Solution to Homework Problem 3.1(Defining Electric Field Direction) Problem: What is the direction of electric field defined to be? Select One of the Following: (a) The direction of higher energy. (b) The direction of higher force. (c-Answer) The direction of the force on a positive charge. (d) The direction a charged object will tend to move. Solution The direction of electric field is defined to be the direction of electric force on a positively charged particle. Total Points for Problem: 3 Points Solution to Homework Problem 3.2(Electric Field of Line Charge) Problem: An infinite line charge with charge density = 2 . 10- 7 C m runs down the y-axis. What is the electric field at the point P , 5 . 0cmx? Select One of the Following: (a) 7 . 2 10 5 N C x (b-Answer) 7 . 2 10 4 N C x (c) 7 . 2 10 5 N C y (d) 7 . 2 10 4 N C y (e) 3 . 6 10 4 N C z Solution The electric field of an infinite line charge is given by vector E = 2 r r. In this case, r = x and r = 5cm , by observation giving vector E P = 2 10- 7 C m 2 (8 . 85 10- 12 C 2 Nm 2 )(0 . 05m) x vector E P = (7 . 2 10 4 N C )x Total Points for Problem: 3 Points 1 Solution to Homework Problem 3.3(Using a vector field) Problem: The electric field in a region of space is given by vector E ( vector r ) = (100 N C , 50 N C ,- x 2 ( N C / m 2 )) . Note, this electric field can not be generated by a static charge, were just playing with vector functions. Assume two significant figures. (a)Compute the electric field at a point 5m along the positive x-axis. Select One of the Following: (a) (100 N C , 100 N C ,- 5 N C ) (b-Answer) (100 N C , 50 N C ,- 25 N C ) (c) (- 250 N C , 50 N C ,- 25 N C ) (d) (- 2500 N C , 50 N C ,- 25 N C ) (e) (- 25 N C , 50 N C ,- 25 N C ) (b)Compute the strength(magnitude) of the electric field at this point....
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