Thursday, August 7, 2014

reference frames - Choice of Origin in Multipole Expansion in Electrostatics


In a multipole expansion in electrostatics, how do we select the origin? For instance, if there is a linear continuous distribution of charge +Q (say from x=a to x=+a). Is there any rule such as: midpoint (z = Zero in this case). For opposite charges does it have to be the centre of the charge distribution where effective charge = zero?




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classical mechanics - Moment of a force about a given axis (Torque) - Scalar or vectorial?

I am studying Statics and saw that: The moment of a force about a given axis (or Torque) is defined by the equation: $M_X = (\vec r \times \...