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Saturday, March 17, 2012

How to Find Terminal Velocity of Conducting Loop Falling into B-field

Here is a different type of induction problem. This has to do with the long aluminum tube we have in the lab, and even though it is non-magnetic, a falling magnet in the tube falls with a terminal velocity. Huh?! The reason for this is as the magnet moves, it is changing flux in the loop. This induces a voltage (Faraday) and therefore a current (Ohm). In a tube these are called eddy currents.

But those currents then feel a force since they are in a magnetic field. This is F = Il x B. The force is upward, trying to stop the motion and therefore stopping the change in flux (Lenz). The mathematics turn out to be identical to that of a sky diver with air friction! We will get an exponential solution, and a terminal velocity. Check it out!


  1. Hello

    I’m working on game development magazine – Game Coder Mag Physics – aimed mostly at professionals and those who study to work in the field of game development in the future.

    I’m looking for authors for the next issue devoted to collision detection. But if You would like to chose other topic there won't be a problem. Please let me know if you'd be interested in writing an article for the magazine by mail

    Adam Aleksander Robakiewicz

  2. Fluid Dynamics
    Viscosity, drag force, terminal velocity, turbulent and laminar flow, equation of continuity