electric dipole moment
C2Formal, Technical, Academic
Definition
Meaning
A measure of the separation of positive and negative electrical charges in a system of charges, characterized as a vector quantity pointing from the negative to the positive charge.
In physics and chemistry, a fundamental property of a charge distribution that describes its inherent polarity and its interaction with external electric fields. It is crucial for understanding molecular structure, intermolecular forces, and spectroscopic behavior.
Linguistics
Semantic Notes
Strictly a scientific term. The concept is always quantitative (measured in debyes or coulomb-metres). Often shortened to 'dipole moment' in context, with 'electric' implied.
Dialectal Variation
British vs American Usage
Differences
No significant lexical differences. Spelling follows national conventions within accompanying text (e.g., 'centre' vs. 'center').
Connotations
Identical technical connotations in both dialects.
Frequency
Exclusively used in technical/scientific contexts with equal frequency in both UK and US academic English.
Vocabulary
Collocations
Grammar
Valency Patterns
The electric dipole moment of [NOUN PHRASE] is...To calculate/measure/determine the electric dipole moment.An electric dipole moment arises from...A molecule with a permanent electric dipole moment.Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “No idioms exist for this technical term.”
Usage
Context Usage
Business
Not used.
Academic
Core term in physics, chemistry, and materials science lectures, textbooks, and research papers.
Everyday
Never used in everyday conversation.
Technical
Precise term used in quantum mechanics, electrostatics, spectroscopy, and molecular modelling.
Examples
By Part of Speech
verb
British English
- The molecule does not 'electric dipole moment' – it *has* one. No verb form exists.
American English
- The molecule does not 'electric dipole moment' – it *has* one. No verb form exists.
adverb
British English
- dipolarly (extremely rare, technical)
American English
- dipolarly (extremely rare, technical)
adjective
British English
- dipolar
- polar
- electric-dipole-related (as a compound modifier)
American English
- dipolar
- polar
- electric-dipole-related (as a compound modifier)
Examples
By CEFR Level
- Not applicable for A2 level.
- Water has an electric dipole moment because its atoms are not arranged in a straight line.
- Scientists can measure the electric dipole moment of some molecules.
- The electric dipole moment is a vector quantity that points from the negative to the positive charge.
- A molecule's polarity is directly related to the magnitude of its permanent electric dipole moment.
- The observed Stark shift in the spectrum allowed for the precise calculation of the molecule's electric dipole moment.
- Despite being symmetrical, the transient electric dipole moment induced by the external field was significant.
Learning
Memory Aids
Mnemonic
Think of a magnet: its north and south poles are separated, creating a magnetic moment. Similarly, an ELECTRIC DIPOLE MOMENT is for electric charges: a separated + and - charge creates this 'electric twist'.
Conceptual Metaphor
A SEESAW OF CHARGE (the greater the imbalance and distance, the stronger the 'moment' or turning force in an electric field).
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid literal translation like *'электрический момент диполя' which is less common. The standard term is 'электрический дипольный момент'.
- Confusion with 'момент' as a point in time vs. a physical moment (moment of force). Here it is the physical 'момент'.
- Do not omit 'электрический' when contrasting with 'magnetic dipole moment' ('магнитный дипольный момент').
Common Mistakes
- Pronouncing 'dipole' as /ˈdɪpəl/ (like 'dippel') instead of /ˈdaɪpəʊl/ ('die-pole').
- Treating it as a scalar instead of a vector quantity in descriptions.
- Using it to refer to temporary charge fluctuations in non-polar molecules without specifying 'induced'.
Practice
Quiz
What is the SI unit for electric dipole moment?
FAQ
Frequently Asked Questions
In most chemistry/physics contexts, 'dipole moment' implicitly means 'electric dipole moment'. However, precisely, 'dipole moment' can be electric or magnetic, so 'electric' is used for clarity when needed.
A ground-state atom in isolation typically has a spherically symmetric charge distribution and thus no permanent electric dipole moment. However, an external electric field can induce a temporary one.
A permanent dipole moment exists even in the absence of an external field due to the molecule's inherent structure (e.g., HCl). An induced dipole moment is created temporarily when an external electric field distorts the electron cloud of a normally non-polar molecule.
It has both a magnitude (the product of charge and separation distance) and a direction (from negative to positive charge). This directional nature is crucial for understanding how the dipole aligns with or responds to external electric fields.