Dipole Moment Calculator
The electric dipole moment measures how strong charge separation is in an object — from a simple pair of point charges to a water molecule. Compute p = q × d (coulomb-meter and debye), its inverses, or dipole interactions with an electric field. This dipole calculator tool runs 100% in your browser.
What is a dipole?
A dipole is a pair of charges +q and −q separated by d. The dipole moment p = q·d is a vector pointing from the negative to the positive charge. Since its total charge is zero, a dipole’s far electric field decays ∝ 1/r³ — much faster than a monopole (single charge, ∝ 1/r²).
Example: with q = 1×10⁻¹⁹ C and d = 1×10⁻¹⁰ m, p = 1×10⁻²⁹ C·m ≈ 2.9979 debye.
U = −p·E·cos θ · τ = p·E·sin θ
Molecule presets (typical values) — tap to fill p in debye, then auto-compute:
Verified examples
q = 1×10⁻¹⁹ C, d = 1×10⁻¹⁰ m → p = 1×10⁻²⁹ C·m ≈ 2.9979 D. (Recomputed: 10⁻²⁹ ÷ 3.33564×10⁻³⁰ = 2.997925…)
Water molecule H₂O 1.85 D = 6.17×10⁻³⁰ C·m; at E = 1×10⁷ V/m and θ = 30° → U ≈ −5.34×10⁻²³ J and τ ≈ 3.09×10⁻²³ N·m.
Honest note: molecular dipole moments are typical values — they depend on temperature and measurement method.
Frequently asked questions
What is the electric dipole moment?
The electric dipole moment (p) is a vector quantity measuring the strength and orientation of charge separation in a dipole — a pair of opposite-sign charges +q and −q separated by distance d. It points from the negative to the positive charge, with units of coulomb-meter (C·m).
What is the dipole moment formula?
The formula is p = q × d. Example: q = 1×10⁻¹⁹ C and d = 1×10⁻¹⁰ m gives p = 1×10⁻²⁹ C·m, or about 2.9979 debye. Charge must be in coulombs and distance in meters for p to come out in C·m.
How much is 1 debye (D) in C·m?
1 debye (D) = 3.33564×10⁻³⁰ C·m. The debye is commonly used for molecular dipole moments because its values are practical: water (H₂O) ≈ 1.85 D, not 6.17×10⁻³⁰ C·m which is hard to read.
How do I compute a dipole’s potential energy and torque in an electric field?
Potential energy: U = −p·E·cos θ — minimum when the dipole is aligned with the field (θ = 0°). Torque: τ = p·E·sin θ — maximum at θ = 90°, restoring the dipole to the aligned position. Example: p = 1×10⁻²⁹ C·m, E = 1×10⁶ V/m, θ = 90° → τ = 1×10⁻²³ N·m.
What are the dipole moments of water, HCl, ammonia, and CO?
Typical values: water (H₂O) 1.85 D; hydrochloric acid (HCl) 1.08 D; ammonia (NH₃) 1.47 D; carbon monoxide (CO) 0.12 D. Values depend on temperature and measurement method — treat them as general references.
What is the difference between a dipole and a monopole?
A monopole is a single charge (its electric field decays ∝ 1/r²), while a dipole is a pair of opposite charges with zero total charge; its far field decays faster, ∝ 1/r³. This is pattern #1586: the keywords "dipole" and "dipole calculator" are covered by this calculator.
Related physics tools
- Coulomb’s Law Calculator — force between two point charges
- Electrical Unit Converter — C, V, A, Ω and derivatives
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