8.02 Lecture Notes - Lecture 1: Joule, Bisection, Sinj
Document Summary
As you move to large distances r away from a dipole, the electric eld will fall-off as: more rapidly than 1/r^2. Electric dipole moment: two charges p = q r + q r = qaj + (-q)(-aj) = 2qaj. Dipole moment vector point from negative to positive charge. Direction of eld at any point is tangent to eld line at that point. Field lines point away from positive charges and terminate on negative charges. E = e p = 2qa(cos + sin j) Total net force: f = f + f = qe + (-q)e = 0. Torque on dipole: = r x f = p x e. = rf sin( ) = (2a)(qe)sin( ) = pesin p tends to align with the electric eld. Total eld (dipole + background) lines illustrate torque. Connection between dipole eld and constant eld pulls dipole into alignment.
