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Coulomb 's law

  1. Aug 14, 2011 #1
    In the case of two charges separarted at a distance r, the electrical potential energy follows that V=(q1q2)/(4*pi*epslion*r), I want to ask why the dimenision of this equation is not consistent and this equation still has a physical meaning. From a textbook about electricity and magnetism, the equation is often in a form like V= Q/4pi*epslion*r, however, this equation has a dimension consistency . I am confused because initially I want to derive this equation from the common form of Coulombs' law ( F=kq1q2r/|r|^3), but if I follow this form, it would probably give the former equation that is not dimensionally consistent. I wonder if I got any misconception(s) .
  2. jcsd
  3. Aug 14, 2011 #2


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    [tex]V= \frac{Q}{4\pi \epsilon \,r}[/tex] is an electrostatic potential at the point [itex]r[/itex] from the charge [itex]Q[/itex].
    [tex]E= \frac{Q_1Q_2}{4\pi \epsilon \,r}[/tex] is an electrostatic energy of two charges [itex]Q_1[/itex] and [itex]Q_2[/itex] at the distance [itex]r[/itex].

    Check dimensions (units) again! They are consistent.
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