Eddy currents are currents induced in conductors when the magnetic flux through them changes. These currents can oppose motion and create magnetic damping, a useful example of electromagnetic induction and Lenz’s law.
When a conductor moves through a magnetic field—or when a magnetic field moves relative to a conductor—the magnetic flux through the conductor can change. Faraday’s law says that this changing flux induces an emf. If the conductor provides a path for current, the induced current is called an eddy current.
All flashcards
What is an eddy current?
A circulating current induced within a conductor when the magnetic flux through it changes.
How does Lenz’s law determine an eddy current’s direction?
The current’s magnetic effect opposes the change in flux that produced it.
What is magnetic damping?
Motion-opposing drag produced when eddy currents in a conductor interact with a magnetic field.
Why is a conducting plate slowed both entering and leaving a magnetic field?
The changing flux induces currents whose magnetic force opposes the plate’s motion at both boundaries.
How do slots or insulating layers reduce eddy currents?
They interrupt large conducting paths, limiting the size of current loops.
Quiz questions
How does magnetic damping help a nearly friction-free laboratory balance settle?Answer: Eddy currents in a moving conducting disc oppose its oscillations.
How can magnetic damping help separate materials in recycling?Answer: Conductors experience eddy-current drag, while nonmetals continue down the ramp.
How does a typical coil-based metal detector sense nearby metal?Answer: Metal-induced eddy currents alter the current induced in the detector’s secondary coil.
Why can an eddy-current brake not bring a moving vehicle completely to rest by itself?Answer: Its braking force decreases as the vehicle slows, so another system must complete the stop.
How does an induction cooktop heat a conductive pot base?Answer: A changing magnetic field induces currents in the base, heating it.
Based on University Physics Volume 2 by Samuel J. Ling, William Moebs, Jeff Sanny (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.