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Homework Help: Torque on Charges in an Electric Field

  1. Jun 17, 2010 #1
    1. The problem statement, all variables and given/known data

    Two small plastic spheres, one charged to 17 nC and the other to -17 nC, are connected by a 25-mm long insulating rod. Suppose this dipole is placed in a uniform electric field with strength 7.4 x 10^5 N/C. What is the maximum possible torque on the dipole?

    2. Relevant equations

    t = qEL

    3. The attempt at a solution

    t = qEL
    =(17 x 10^-9 C)(7.4 x 10^5 N/C)(2.5 x 10^-2 m)
    =3.15 x 10 ^-4 J
    This can't be right. Is torque measured in Joules? Can somebody please help me out with this problem?
  2. jcsd
  3. Jun 17, 2010 #2


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    Homework Helper

    Your unit is Nm, which is right for torque, not the equivalent J for energy.
  4. Jun 17, 2010 #3
    How about the solution?
  5. Jun 17, 2010 #4


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    Homework Helper

    Looks correct to me.
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