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Magnet falling through a ring

When a magnet falls through a ring, current is induced in the ring. This phenomenon is called electromagnetic induction.

According to Faraday’s law, the induced emf is proportional to the negative of the rate of change of magnetic flux Φ. The direction of the induced current is determined by Lenz’s law, the induced current produces magnetic field which tends to oppose the change in magnetic flux that induces such currents.

The voltage induced when a magnet is falling through a ring is simulated in this experiment, where we model the magnet as a magnetic 'dipole'. The current is visualized by very big 'electrons' that move according to the strength of the current.

Please, complete this set of Minds-On questions:

  • Explain the shape (positive and negative peaks) of the recorded signal.
  • Why the peaks are not symmetric?
  • At which moment was the magnetic flux changing most quickly?
  • What was the total change of magnetic flux during the first half of the magnet’s fall - while it was moving in to the coil?
  • What was the total change of magnetic flux during the second half of the magnet’s fall - while it was moving out of the coil?
  • How could you change the simulation to increase the magnitude of the signal?


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Software Requirements


Android iOS Windows MacOS
with best with Chrome Chrome Chrome Chrome
support full-screen? Yes. Chrome/Opera No. Firefox/ Samsung Internet Not yet Yes Yes
cannot work on some mobile browser that don't understand JavaScript such as.....
cannot work on Internet Explorer 9 and below



Maria Jose Cano; Fremont Teng; Ernesto Martin; Francisco Esquembre - Universidad Murcia; Loo Kang Wee

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Sample Learning Goals


For Teachers



Graph Combo Box

Toggling this box will toggle which graph to display.
(Position Vs Time)

(Velocity Vs Time)

(Voltage Vs Time)

Cool Ring Check Box

Toggling this will toggle if the ring is cooled or not.

North/South is Up Button

Toggling between this button will flip the magnet accordingly.

Ring Size Field Box

Changing this will change the size of the ring.

Free Falling Ball Check Box

Toggling this will toggle the visibility of the free falling ball.
Note that the graphs will also plot those of the free falling ball if checked on.

Toggling Full Screen

Double click anywhere in the panel to toggle full screen.
Note that it won't work if the simulation is running.

Play/Pause, Step and Reset Buttons

Plays/Pauses, steps and resets the simulation respectively.






Other Resources


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