Freezing droplet


A droplet on a deep-frozen surface turns into a conical shape. Scientists of the University of Twente (Physics of Fluids) found out why, by looking into the droplet. Their results are also important for other processes where liquid droplets solidify ‘from the bottom’, like 3D printing.

Universality of Tip Singularity Formation in Freezing Water Drops
A. G. Marín, O. R. Enríquez, P. Brunet, P. Colinet, and J. H. Snoeijer
A drop of water deposited on a cold plate freezes into an ice drop with a pointy tip.
While this phenomenon clearly finds its origin in the expansion of water upon freezing, a quantitative description of the tip singularity has remained elusive. Here we demonstrate how the geometry of the freezing front, determined by heat transfer considerations, is crucial for the tip formation.
We perform systematic measurements of the angles of the conical tip, and reveal the dynamics of the solidification front in a…

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Geothermal Heating and Cooling Systems

gshpGeothermal heating and cooling systems are globally used in many industrial and domestic applications. The source of this energy lies in the interior of our planet, the solar energy received at the surface, and also because of the decomposition of the mineral wealth in the depths of the planet. There have been several ancient remains and proofs of the use of geothermal heating systems. These can be traced to the ancient Indus valley civilization, the Roman empire, and the subsequent periods in human history when civilizations flourished. Presently, its main use is in the generation of electricity.

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How Does a Thermocouple Work?

A thermocouple is a device, which senses temperature by using two different metals joined at one end. This article will tell you more about the functioning, types, and uses of this device.

Thermocouples are largely used in the fields of science and electronics as a temperature sensor, which are quite easy to handle and use. The functioning is based on the Seebeck effect, common in case of electrical conductors, that experiences a temperature gradient along their length. These sensors are simple, rugged, do not need batteries, and have the ability to measure very wide temperature ranges. They consist of two different metals, joined together at one end. Whenever the junction of the two metals is heated or cooled, a voltage can be obtained, that is proportional and can be correlated to the temperature, that was given when the sensor was heated. Thermocouple alloys are usually available as a wire. They are quite cheap, but their main drawback is their accuracy.

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Different Types of Thermometers


Why do you need to measure temperature? Think of all the ways temperature measurement is important in your life. If you know the temperature outside, you know how to dress to go out. If you know the temperature inside your oven, you know if it is hot enough to cook a pizza. You can probably think of many more examples. Different types of thermometers can be used to measure temperatures. Since solids, liquids, and gases usually expand when heated and contract when cooled, almost any substance could be used in a thermometer. The choice usually depends on the way the thermometer will be used…

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Why Can’t We Get Down to Absolute Zero?

Liquid Nitrogen

What is Absolute Zero, and does it really exist anywhere in the universe? Could we ever reach Absolute Zero in real life?

There are all sorts of reasons to be curious about the limits of cold. Maybe you’re an incredibly lame supervillain who uses the power of freezing, and you want to understand the extent of your powers. Or you’re wondering if it would be possible to outrun a wave of cold. Either way, in this week’s “Ask a Physicist” we’ll explore the farthest limits of cold.

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Crickets Make Such Excellent Thermometers!


Unlike renegade mammals that live fast and play by their own thermal rules, cold-blooded reptiles and insects march to the beat of a more universal drum—ambient air temperature. You can see it in the speed at which ants walk and fireflies flash, or hear it in the cadence of a cricket’s love song. Their melodies are so precise, in fact, that you can even measure the temperature outside by how fast they chirp.

Let’s talk a bit about how crickets make their symphony of chirps in the first place. They employ a method known as stridulation…

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