Eddy Currents
Eddy-current strength grows with changing flux and falls when the conductor is laminated or slotted because the current paths gain resistance and lose area.
Why this shows up in the exam
Induction furnaces · Magnetic braking · Metal detectors
Learn the idea
Changing flux creates circulating currents inside bulk conductors. A metal sheet contains many possible closed paths. Changing flux drives currents around those paths; their magnetic effect opposes motion or field change and their resistance produces heat.
🧠 Memory hook: Eddies swirl, heat, and oppose.
Get this one clearly and it pays off every single time it shows up in the paper. 🎯
Formulas & facts to keep ready
- P_heat = I_eddy² R — eddy currents can produce useful or unwanted heating
How to approach it
- 1Identify a bulk conductor
- 2Find the changing flux
- 3Use Lenz's law for the force direction
Common slip-ups that cost marks
- •Calling every induced current an eddy current
- •Thinking laminations remove magnetic flux
- •Ignoring useful applications of eddy-current heating
🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.
Original chapter practice
Original questions for this chapter, not past-paper questions or an exact mapping to this individual concept.
A conducting rod of length 2 m moves at 3 m/s perpendicular to a 4 T magnetic field. Find the motional emf.
More from Electromagnetic Induction and Alternating Currents
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AC Generators and Transformers
AC generators convert mechanical energy to electrical energy using electromagnetic induction, while transformers transfer electrical energy between circuits, often changing voltage levels.
Faraday's Law and Lenz's Law
Faraday's law explains how a changing magnetic field induces an electromotive force (EMF), while Lenz's law determines the direction of the induced current to oppose the change causing it.
Self and Mutual Inductance
Self-inductance is the property of a coil to oppose changes in its own current, while mutual inductance is the ability of one coil to induce EMF in another nearby coil.
Eddy Currents and Applications
Eddy currents are circulating currents induced in conductors by changing magnetic fields, leading to energy loss and effects like electromagnetic damping.
Motional EMF
Motional EMF is the voltage induced in a conductor moving through a magnetic field, depending on the speed, length, and orientation of the conductor.