A student drops a strong cylindrical neodymium magnet vertically down the center of a thick-walled, non-magnetic copper tube. Which statement correctly describes the subsequent motion of the magnet and the physical principle governing this behavior?
The magnet falls freely with acceleration ggg because copper is non-magnetic and cannot support electromagnetic induction, demonstrating that Lenz's law only applies to ferromagnetic materials.
The moving magnet induces circular eddy currents in the copper tube. These currents create a magnetic field that exerts an upward retarding force on the magnet, which is a consequence of Lenz's law and the conservation of energy.
The moving magnet induces a static charge separation along the length of the tube, creating an electrostatic force that balances gravity, which is a consequence of Coulomb's law.
The moving magnet induces eddy currents in the copper tube that create a magnetic field pulling the magnet downwards, causing it to accelerate faster than free fall, which demonstrates the conservation of linear momentum.
34 exam-style questions on OCR A A Level Physics Electromagnetism, covering Magnetic fields, Motion of charged particles, and Electromagnetism. Each one has a worked solution and a mark scheme showing where the marks go.