= Solution
An <electric dipole> consists of opposite charges separated by a small displacement, with <electric dipole moment> $\mathbf p=q\mathbf d$ directed from negative to positive. At distances large compared with its size,
$$
\Phi=\frac{\mathbf p\cdot\widehat{\mathbf r}}{4\pi\epsilon_0r^2},\qquad
\mathbf E=\frac{3(\mathbf p\cdot\widehat{\mathbf r})\widehat{\mathbf r}-\mathbf p}{4\pi\epsilon_0r^3}.
$$
The net charge term vanishes; the field decays faster than a monopole field. In an imposed slowly varying <electric field>,
$$
\boldsymbol\tau=\mathbf p\times\mathbf E,\qquad U=-\mathbf p\cdot\mathbf E,\qquad
\mathbf F=\nabla(\mathbf p\cdot\mathbf E)
$$
for a permanent fixed dipole. A uniform field produces a <torque> but no net <force>. For a linear induced dipole $\mathbf p=\alpha\mathbf E$, the interaction <energy> is instead $-\alpha E^2/2$, because building the dipole also costs <energy>.
A small planar <current loop> has <magnetic dipole moment> $\boldsymbol\mu=IA\widehat{\mathbf n}$, with the normal fixed by the <right-hand rule>. Outside the source,
$$
\mathbf B=\frac{\mu_0}{4\pi r^3}[3(\boldsymbol\mu\cdot\widehat{\mathbf r})\widehat{\mathbf r}-\boldsymbol\mu],\qquad
\boldsymbol\tau=\boldsymbol\mu\times\mathbf B,\qquad U=-\boldsymbol\mu\cdot\mathbf B.
$$
<Magnetic field> lines form closed loops; a current-loop dipole does not require <magnetic monopoles>. \b[Dipole moments describe the leading directional field of a neutral localized source], and their <torques> explain alignment in external fields.
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