larmor precession
C2 (Very Low Frequency)Exclusively Technical/Scientific
Definition
Meaning
The slow, circular motion of the axis of a spinning object (especially an atomic nucleus or electron) when placed in an external magnetic field, where the precession frequency is proportional to the field strength.
In a broader physics context, it can refer to the precession of any magnetic moment in a magnetic field. It's foundational for technologies like Magnetic Resonance Imaging (MRI) and nuclear magnetic resonance (NMR) spectroscopy.
Linguistics
Semantic Notes
A compound noun naming a specific physical phenomenon. It is always used as a singular noun. The concept is named after physicist Sir Joseph Larmor.
Dialectal Variation
British vs American Usage
Differences
No significant lexical differences. Spelling follows standard UK/US conventions for surrounding text (e.g., 'behaviour' vs. 'behavior'). The term itself is invariant.
Connotations
None beyond its precise scientific meaning.
Frequency
Identically rare and confined to advanced physics, chemistry, and engineering contexts in both varieties.
Vocabulary
Collocations
Grammar
Valency Patterns
The [magnetic moment/spin] undergoes Larmor precession in a [magnetic field].The frequency of the Larmor precession is given by...Larmor precession of the [nuclei/electrons] causes...Vocabulary
Synonyms
Neutral
Weak
Usage
Context Usage
Business
Not used.
Academic
Core concept in advanced physics, physical chemistry, and electrical engineering courses and research, particularly in quantum mechanics, NMR, and MRI theory.
Everyday
Not used.
Technical
Fundamental in papers and manuals related to NMR spectroscopy, MRI technology, spintronics, and quantum computing.
Examples
By Part of Speech
verb
British English
- The magnetic moment will precess around the field direction at the Larmor frequency.
American English
- The spins precess at the Larmor frequency in the external field.
adjective
British English
- The observed frequency matched the calculated Larmor frequency.
American English
- We measured the Larmor precession rate directly.
Examples
By CEFR Level
- In an MRI scanner, the hydrogen nuclei in your body undergo Larmor precession.
- The phenomenon of Larmor precession is fundamental to understanding how nuclear magnetic resonance spectroscopy works, as the precession frequency is directly proportional to the applied magnetic field strength.
Learning
Memory Aids
Mnemonic
Imagine a LARge spinning gyroscope (gyr) on a table. When you push it with a MAGnet, it starts to wobble or 'precess' in a slow circle. LAR-MOR precession: LARge Magnet-induced wobble ORbit.
Conceptual Metaphor
A spinning top wobbling when pushed sideways.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid translating as 'прецессия Лармора' in non-specialist texts without immediate explanation, as it is opaque to general readers. It is a fixed term.
- Do not confuse with 'прецессия' alone, which is a broader term for any rotational axis movement.
Common Mistakes
- Incorrectly capitalising 'precession' (it is not a proper name).
- Mispronouncing Larmor as 'lar-MORE' instead of 'LAR-mor'.
- Using it as a verb (e.g., 'The nuclei larmor precess').
Practice
Quiz
What does Larmor precession describe?
FAQ
Frequently Asked Questions
It has both a classical explanation (for a macroscopic magnetic moment) and a quantum mechanical one. The underlying principle is the same, making it a unifying concept.
It is the core physical principle behind Magnetic Resonance Imaging (MRI) machines used in hospitals and NMR spectrometers used in chemistry labs and pharmaceutical research.
Sir Joseph Larmor (1857–1942) was an Irish physicist and mathematician who made significant contributions to electromagnetism and thermodynamics.
The Larmor angular frequency ω is given by ω = γB, where γ is the gyromagnetic ratio (a constant for a given particle) and B is the magnetic field strength.