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Homework Help: Movement through an electric field

  1. Jul 1, 2010 #1
    1. The problem statement, all variables and given/known data

    A constant electric field of magnitude E = 120 V/m points in the positive x-direction. How much work (in J) does it take to move the charge Q =11 μC from x1 = -67 m, y1 = -36 m, to x2 = 98 m, y2 = 75 m?

    2. Relevant equations
    You see thats the problem... I have no idea


    3. The attempt at a solution
    Its not much of an attempt but i know work is force times displacement right? So its just the force needed to move it times how far it is moved. But i dont know how to find the force needed to move it
     
  2. jcsd
  3. Jul 1, 2010 #2
    There are two ways to approach this.

    First you can determine the voltage difference between the two points. Since voltage is energy (or work) per unit charge, you will take the voltage difference times the charge to find the work done. Remember that voltage is the line integral of electric field over distance (vectorially with dot product).

    Second, you can use the fact that electric field is force per unit charge. Hence electric field times charge tells you the force. You already described how to use force to calculate work done.

    Try both methods and make sure you get the same answer either way. Remember that force and electric field is a vector, so be careful with direction and vector components.
     
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