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Unformatted text preview: Solution for Homework 14 Introduction to Magnetic Fields Solution to Homework Problem 14.1(Magnetic Field of Pith Ball) Problem: A pith ball is charged with an electrophorus to 1nC and shot along the x-axis at 100 m s in the + x direction. What is the magnitude of the magnetic field at (0 , 1cm , 0) when it reaches the origin? Select One of the Following: (a-Answer) 1 10 10 T z (b) 2 10 10 Ty (c) 4 10 7 T z (d) 3 10 11 T z (e) 2 10 10 Tx Solution The magnetic field of a moving charge is vector B = 4 qvectorv r 10 r 2 10 where the vector vector r 10 points from the location of the charge to the location where the field is computed, q = 1nC is the charge, vectorv = 100 m s x is the velocity. When the charge reaches the origin, vector r 10 = (0 , 1cm , 0) , r 10 = 1cm , and r 10 = y . Compute the cross product, vectorv r 10 = 100 m s (x y) = 100 m s z , where we use the right hand rule to solve the cross product. Substitute into the complete expression for vector B giving vector B = 4 q r 2 10 ( vectorv r 10 ) = parenleftbigg 4 10 7 Tm A 4 parenrightbiggparenleftbigg 1 10 9 C (0 . 01m) 2 parenrightbiggparenleftbigg 100 m s z parenrightbigg vector B = 1 10 10 T z 2 point(s) : Magnitude 1 point(s) : Direction. Total Points for Problem: 3 Points Solution to Homework Problem 14.2(Right Handed Coordinate Systems) Problem: If the y axis points to the right of the page and the z axis points to the top of the page, what direction does the x axis point? Select One of the Following: (a) To the left of the page....
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