Cold Magnetic Ballet in PhysLab
In an absolutely stunning display of beauty, a drop of liquid oxygen, and its tail of gaseous oxygen, is seen orbiting a magnet almost exactly like a distant icy comet that dives into the inner solar system, developing a tail of dust and ice, making a tight U-turn around the Sun, only to slip back into the darkness of the abyss.
Liquid nitrogen is no stranger to pop culture and is considered a darling ingredient for many fun science experiments. This reputation is due to its extremely cold temperature. When liquid nitrogen is poured into a copper cone, the copper runs so cold that oxygen from thin air surrounding the metal condenses onto the tip of the cone, creating droplets that soon start dripping. In an interesting digression, Anne Hathaway, a celebrated American actress is seen as the ‘White Queen making perfume’, using a cone that’s eerily similar to this experiment!
This is no different from glass gathering water droplets when a cold beverage is poured in. Science – it works no matter if it’s cold water or liquid nitrogen! These droplets run off an inclined plane on to a black sheet, which hides a strong magnet beneath. As the drops slide on to the black sheet, they appear to deflect at varying degrees. How this reminds us of Rutherford’s experiment where electrons would deflect because of the presence of a dense nucleus in the middle of atoms. Indeed, the beauty of this experiment is that it is a low-energy version of Rutherford’s experiment.
This display of magnetic ballet is in part courtesy of oxygen’s weak, but observable response to magnetic fields without retaining permanent magnetism. We say that oxygen is paramagnetic. In addition to this, from the time the drop falls off the cone to getting deflected over the black sheet, it never touches any surface – the liquid oxygen drop levitates! This is one strange experiment. This can be explained through what is known as the Leidenfrost Effect. Simply put, the bottom of each drop of liquid oxygen vapourises very quickly, creating an ‘Aladdin’s magic carpet’ of gaseous oxygen that keeps the drop afloat. Fascinating! Conventional methods of demonstrating this magical property of oxygen involve bulky magnets and expensive setups. At PhysLab, the experiment demonstrated the use of cheaper, simpler materials without significant compromise on the intended output. The beauty of physical laws is in their consistency. If they’re true on a desk in PhysLab, they must also be true in the remote reaches of the universe.
Dr. Sabieh Anwar, along with physics major Mr. Abdullah Irfan helped develop this experiment. The data from this experiment was recorded and analysed by students at the PhysLab.
Their detailed analysis can be seen here: https://physlab.org/experiment/steering-paramagnetic-leidenfrost-drops-in-an-inhomogeneous-magnetic-field/