lenz's law
Very LowTechnical / Academic
Definition
Meaning
A fundamental law of electromagnetism stating that an induced electromotive force (emf) and the induced current it creates will always oppose the change in magnetic flux that produced it.
A principle in physics describing the direction of an induced current, essentially a consequence of the law of conservation of energy applied to electromagnetic induction. It ensures that energy cannot be created from nothing; work must be done to change the magnetic field.
Linguistics
Semantic Notes
Exclusively used in physics, specifically electromagnetism and electrical engineering. It is a proper noun referring to a specific law named after Heinrich Lenz. It describes a reactive, oppositional force.
Dialectal Variation
British vs American Usage
Differences
No significant differences in meaning or usage. Spelling of 'law' and possessive forms are identical. The 'z' in 'Lenz' is standard in both.
Connotations
Purely technical, with no cultural or idiomatic connotations in either variety.
Frequency
Frequency is identical and confined to scientific/engineering contexts in both regions.
Vocabulary
Collocations
Grammar
Valency Patterns
[Subject] obeys/violates Lenz's law.Lenz's law predicts/shows that [clause].According to Lenz's law, [observation].Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “(none)”
Usage
Context Usage
Business
Not used.
Academic
Core concept in university-level physics and electrical engineering courses.
Everyday
Not used.
Technical
Essential in designing electric motors, generators, transformers, and analyzing electromagnetic phenomena.
Examples
By Part of Speech
verb
British English
- The induced current will always oppose, as Lenz's law dictates.
- The experiment beautifully lenzes the law—the coil's motion is resisted.
American English
- The apparatus is designed to Lenz-law the magnetic field change.
- You can see the ring 'lenz' away from the approaching magnet.
adverb
British English
- (Not used)
American English
- (Not used)
adjective
British English
- (Rare) The Lenzian opposition was clearly visible.
- We observed a Lenz's-law effect in the circuit.
American English
- (Rare) The setup demonstrates a Lenz's-law-type reaction.
- This is a classic Lenzian response.
Examples
By CEFR Level
- (Not applicable at this level)
- Scientists have a law called Lenz's law about magnets and electricity.
- When a magnet moves near a wire, it can make electricity flow, and Lenz's law says this flow will fight the magnet's movement.
- According to Lenz's law, the direction of the induced current in a loop will always be such that it opposes the change in magnetic flux through the loop.
- You can demonstrate Lenz's law by dropping a strong magnet through a copper pipe; it falls slowly because the induced currents create an opposing magnetic field.
- The elegant formulation of Lenz's law provides the necessary sign in Faraday's law of induction, ensuring consistency with the principle of conservation of energy.
- In analyzing the eddy currents in the braking system, the engineer applied Lenz's law to predict the direction of the opposing force on the rotating disk.
Learning
Memory Aids
Mnemonic
Think of Lenz's law as the universe's way of saying 'No!' to a change in magnetic field. The induced current creates its own magnetic field that fights the change, like a stubborn child resisting being pushed.
Conceptual Metaphor
ELECTROMAGNETIC OPPOSITION IS INERTIA / RESISTANCE. A change in magnetic conditions meets an opposing force, analogous to mechanical inertia resisting a change in motion.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- The possessive 's' must be retained: It's "Lenz's law" (Закон Ленца), not "Lenz law."
- Avoid translating it descriptively in English text; use the standard name "Lenz's law."
Common Mistakes
- Misspelling as "Lenz' law" (though technically debatable, 'Lenz's' is standard).
- Confusing it with Faraday's law (which gives the magnitude of induced emf, while Lenz's gives the direction).
- Incorrectly stating it creates the change, rather than opposing it.
Practice
Quiz
What fundamental conservation principle is Lenz's law a direct consequence of?
FAQ
Frequently Asked Questions
It was formulated by the Baltic German physicist Heinrich Friedrich Emil Lenz in 1834.
It is often considered the directional part of Faraday's law of induction. The negative sign in the mathematical form of Faraday's law (emf = -dΦ/dt) embodies Lenz's law.
Yes. Electromagnetic braking in trains and rollercoasters uses Lenz's law. A moving magnet near a conductor induces currents that create a magnetic field opposing the motion, slowing the vehicle without physical contact.
If induced currents reinforced the change that created them, it would lead to a perpetual increase in energy from nothing (a positive feedback loop), violating the conservation of energy. Motors could run without input power.