Calculate electric dipole fields, potentials, torque, and energy. Convert between C·m and Debye units with distance-dependent field analysis.
An electric dipole consists of two equal and opposite charges separated by a small distance, characterized by its dipole moment p = qd. Dipoles are fundamental in physics and chemistry—from individual molecules like water (permanent dipoles) to induced dipoles in dielectric materials and antenna theory.
The electric field of a dipole decreases as 1/r³, much faster than the 1/r² field of a single charge. This rapid falloff means dipole interactions are significant only at short range, which has profound implications for molecular forces, dielectric behavior, and electromagnetic radiation.
This calculator computes the complete electric dipole picture: dipole moment in both SI units (C·m) and Debye, axial and perpendicular electric fields, potential, torque and energy in an external field, and field decay profiles with distance. It is useful when you want to connect the textbook equations to molecular-scale examples and see how quickly the field falls away with distance. Keeping the units, geometry, and field outputs together also makes it easier to sanity-check order-of-magnitude results.
Electric dipole problems mix unit conversion, geometry, and rapidly changing field strength, which makes them easy to misread when working by hand. This calculator keeps the dipole moment, field, potential, torque, and energy in one view so you can compare molecular examples, check homework steps, or sanity-check order-of-magnitude estimates quickly.
Dipole moment: p = q × d Axial field: E = 2kp cos(θ) / (εr × r³) Perpendicular field: E = kp sin(θ) / (εr × r³) Potential: V = kp cos(θ) / (εr × r²) Torque: τ = p × E × sin(θ) Energy: U = −p · E = −pE cos(θ)
Result: p = 1.602×10⁻²⁹ C·m = 4.80 D, E_axial = 2.88×10⁸ V/m
An elementary charge separated by 1 Å gives a dipole moment of 4.80 Debye. At 1 nm on axis, the electric field is about 2.88×10⁸ V/m, comparable to intermolecular field strengths.
The compact dipole equations work best when the observation distance is much larger than the separation between the charges. If the point of interest is too close to the actual charges, the exact two-charge field is more accurate than the dipole approximation. That is why the distance input matters as much as the dipole moment itself.
Axial and perpendicular field expressions are not interchangeable. The field and potential depend on the observation angle, and the torque depends on the angle between the dipole and the external field. Use the calculator to compare the same dipole at different orientations so the geometry becomes more intuitive instead of feeling like a memorized formula.
Molecular dipoles are often quoted in Debye, while electromagnetic calculations in SI use coulomb-meters. Converting between the two is routine, but it is also a common source of factor errors. The medium permittivity matters as well, because the same dipole produces a much weaker field in a high-permittivity environment than it does in vacuum.
The Debye (D) is a CGS unit for dipole moment: 1 D = 3.336×10⁻³⁰ C·m. Water has a dipole moment of about 1.85 D. Most polar molecules range from 0.5 to 11 D.
At large distances, the fields from the positive and negative charges nearly cancel. The leading-order surviving term is proportional to 1/r³, making dipole interactions short-range compared to monopole (1/r²) interactions.
An external uniform field exerts a torque τ = p×E×sin(θ) that tends to align the dipole with the field. The equilibrium position is θ = 0 (aligned), and the maximum torque occurs at θ = 90°.
Yes, polar molecules like H₂O (1.85 D), HCl (1.08 D), and NH₃ (1.47 D) have permanent dipole moments. Symmetric molecules like CO₂ and CH₄ have zero net dipole moment.
When a nonpolar atom or molecule is placed in an electric field, the electron cloud shifts relative to the nucleus and creates an induced dipole. Its size depends on field strength and the polarizability of the material.
The relative permittivity (εr) of the medium reduces the dipole field by a factor of εr. In water (εr ≈ 80), the dipole field is 80 times weaker than in vacuum.