The Leidenfrost Effect is a phenomenon in which a liquid drop levitates on a surface that is significantly hotter than its boiling point. When we create Leidenfrost drops using a paramagnetic liquid, such as oxygen, we end up with liquid drops that hover above a surface with negligible friction, and since oxygen is paramagnetic, can be controlled by a magnetic field.
|Software Code||Tracker (Download)|
|Sample Results||Student report Fall 2018|
|Hardware Manual||Photograph of grid (white grid lines on black background). Print on A4 with 1200 dpi resolution|
|Version||April 22, 2019 Version 2019-v1|
Further Readings and References
- Ch 9: Molecular Orbitals General Chemistry , D. A. McQuarrie, P. A. Rock, E. B. Gallogly, Ethan B., , Fourth Edition 275-277 , (2011).
- Magnetic control of Leidenfrost drops Physical Review E , K. Piroird, C. Clanet and D. Quere, , 85 , (2012).
- Central Force Motion An Introduction to Mechanics , D. Kleppner and R. Kolenkow, 378-381 , (1973).
The copper cone is 10cm in height and 10cm in diameter. It holds enough liquid nitrogen to get a supply of liquid oxygen drops for around a couple of minutes. Underneath the tip of the cone is an aluminium bar with a depression along it’s axis. This is to make sure that the drop moves in a straight line as it enters the horizontal sheet. It allows us to vary the initial displacement of the drop (as explained in the video). This sheet is made of plexiglass, which is a cheap solution, but has some problems. The scratches on the surface of this sheet are very prominent in light, so we use a permanent marker to reduce light reflecting from the scratches. The screws near the corners of the sheet allow us to make sure that the sheet is horizontal. This is to ensure that the only force affecting the motion of the drops is the magnetic force. However, since this is a low cost setup and we only ensure that the sheet is horizontal using a spirit level, gravity does affect drops at very slow velocity. The plexiglass walls around the cone ensure that very little nitrogen vapours enter the recording area and makes sure the video recordings are clear and easy to analyse.
We need to make sure that we make no contact with any cold surface during the experiment. We use gloves for handling the glass that is used to pour liquid nitrogen. The cone must not be touched during the experiment, and even after the nitrogen has evaporated. The aluminium bar is not cold enough to be dangerous, but should still preferably not be touched with bare hands. The copper cone should be stable enough so that it can’t be accidentally tipped over while performing the experiment.