# Tag Info

7

The noise is either from the AC electricity, which would be a 60Hz buzzing, or from small bubbles forming on the heating element itself. When the electricity stops, both the buzzing and the bubble formation will stop as well. Bubbles create sound due to quickly expanding from a small nucleus. Here's a book I found with a section on noise from bubble ...

6

The real issue is that the cup wasn't really full so that adding anything more would make it spill. You can clearly see the the level slowly growing above the top of the cup, as would be expected due to surface tension. Eventually another coin finally exceeded the limit, and a little water spilled. There is really nothing extraordinary going on here. ...

4

The correct answer is that Surface tension prevents the formation of small water droplets. You see, as the surface energy is proportional to the droplet area ($r^2$) and the bulk energy - to its volume ($r^3$), their ratio ($1/r$) will rise to infinity as the droplet radius $r$ goes to zero. Therefore, the droplet cannot grow steadily from $r=0$. Even below ...

3

The mechanism by which lightning is produced is complex and imperfectly understood, but we know moisture is important in two respects: Heat is released when water vapor in the air condenses into liquid drops, and this heat helps provide energy to the thunderstorm. Interactions between supercooled liquid water droplets and ice crystals in the upper ...

3

The circles are droplets of fat (triglycerides: triesters of glycerol and fatty acids). The two phases (water and fat) are immiscible because the water molecules are more attracted (hydrogen bonded) to each other than to the fat molecules. Absent gravity, energy would be minimized by the droplets being spherical, but gravity flattens the droplets. The ...

1

I am not aware of a better name for this sort of point in the scientific literature. It doesn't exactly shock me if you refer it as an eutectic point, but you'd have to explain it in its first occurrence in the text. Otherwise, just assign a letter to it (just avoid “lambda point”!), and use that throughout your paper.

1

Your kettle needs incoming energy from the heating element to turn water in to steam. Steam bubbles forming and collapsing make the familiar sound. Early on many of the steam bubbles don't make it to the top because they cool off when they rise away from the heating element. This is why the familiar rumbling sound starts way before the water boils. The ...

1

Whenever it seems like two water levels should be equal but aren't, either there is a physical restriction preventing flow (like a dam keeping upstream waters higher than downstream, or surface tension causing meniscuses or capillary action), or there is energy being expended to put water back upstream as fast as gravity is pulling water downstream. In a ...

1

As DavePhD has explained, the water would never be warmer than the metal. As you waited a long time, you can safely assume they are at the same temperature. But, why do they feel different? Your hands are warm, and when touching a thermal insulator, such as wood, they will quickly transfer energy and heat up the surface of what you are touching, so it feels ...

1

The generation of waves by wind is still an open question. Jeffrey's (1925) made a prediction based on wave shadowing, that is, he proposed that wind over waves would lead to higher pressure over the troughs and lower pressure over the crests, leading to wave growth. It turns out the theoretical growth rates for waves, based on this mechanism, are much too ...

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