Category: Physics

Understanding the Science Behind Refrigeration

by Megan Ray Nichols 

How many times have you gotten up, opened your fridge, looked in for a minute for something to eat, then closed it again without taking anything out today? If we discount the fact that leaving the fridge door open wastes up to 7 percent of the appliance’s energy use when was the last time you thought about your fridge or your air conditioner and how they work to keep your home and snack food cool? How did the milk in your fridge make it from the cow that created it to your home without spoiling? Let’s take a closer look at the cool (pun intended) science behind refrigeration that we so often take for granted.

Why is Refrigeration Important?

We all know that we keep our milk in the fridge to keep it from spoiling, but how does keeping it cold make sure that you’ve got a fresh dairy topper for your morning Frosted Flakes?

We’ve been keeping food cold since prehistoric times. Even cave dwellers realized that if they kept their food in a cool cave or packed it in the snow, it would last longer. Thankfully, we don’t have to wait for a snow day to keep our food cold these days — most homes in developed countries have at least one refrigerator, with 23 percent having two or more.

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Why Do Pipes Freeze in Winter?

by Megan Ray Nichols 

It’s one thing that no homeowner wants to deal with, but it’s often the reality during cold winter months — frozen pipes. In addition to cutting off water to the home, these pipes can also burst, causing water damage. Why do pipes freeze in the winter, and what can you do to prevent them from getting cold enough to freeze? What should you do if the pipes burst? Here are some tips and tricks to help you get through the winter with your plumbing intact.

Why Do They Freeze?

First, why do pipes freeze?

Like most things filled with water, they freeze when the temperature drops below the freezing point of water — 32 degrees Fahrenheit or 0 degrees Celsius.

With pipes, there are two more variable to consider — movement and expansion. It’s harder for water to freeze if it’s in motion. That’s why lakes will freeze at 32 degrees, but it takes much lower temperatures to solidify rivers and waterfalls.

If a section of your pipe starts to freeze, the water expands. This behavior is an anomaly in nature because most liquids don’t grow when they solidify. Water, however, will become denser until it reaches a point just before freezing, then it will start to expand again. In a confined space like the inside of a pipe, this extra pressure doesn’t have anywhere to go, so it will cause the tube to split.

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Newtonian vs. Non-Newtonian Liquids

By Megan Ray Nichols

If you’ve seen any viral videos in the last few years, you’re probably familiar with the concept of non-Newtonian fluids — liquids that are fluid when moving slowly but when struck with force, they take on a solid consistency. Videos have gone viral of people filling entire swimming pools with a mixture of water and cornstarch, allowing them to literally run across the surface of the water. What is the difference between a Newtonian fluid and its non-Newtonian counterpart, and where might you encounter these fluids in your daily life?’

Newtonian vs. Non-Newtonian Liquids

First, what is the difference between Newtonian and non-Newtonian fluids?

Newtonian fluids have a constant viscosity that doesn’t change, no matter the pressure being applied to the fluid. This also means they don’t compress.

Non-Newtonian fluids are just the opposite — if enough force is applied to these fluids, their viscosity will change. These fluids are broken up into two categories — dilatants, which get thicker when force is applied, and pseudoplastics, which get thinner under the same circumstances.

These can be further broken down into rheopectic and thixotropic categories. Rheopectics work like dilatants in that they get thicker when force is applied. Thixotropic materials get thinner, like pseudoplastics do. The difference here is that the latter two categories are time dependant. The viscosity doesn’t change immediately but changes slowly over time as more and more force is applied.

Newtonian Fluids in Daily Life

These fancy names might sound like something out of a science fiction novel, but they’re really just the scientific names for things you encounter in your daily life. What Newtonian fluids have you encountered today?

If you took a shower this morning or had a drink, then you’ve already encountered the most common Newtonian fluid — water! Water does not change viscosity no matter how much pressure you put on it — it also cannot be compressed, so the amount of pressure you can put on water as a Newtonian fluid is negligible.

Other common Newtonian fluids include mineral oil, alcohol and gasoline.

Non-Newtonian Fluids in Daily Life

For this section, we’re going to break it down into the four categories of non-Newtonian liquid that we listed above.

Dilatants are probably the most well known nonnewtonian fluids. They become thick or almost solid when force is applied to them and are made up of water mixed with other materials. Oobleck, the colloquial name for a mixture of water and cornstarch, is probably the most well-known, but quicksand and silly putty also fall into this category.

Pseudoplastics might not sound very appetizing, but you probably have a bottle of one in your fridge right now. That’s right — ketchup is a non-Newtonian fluid. The fact that the viscosity changes as each new ingredient is added to the mix makes it tricky to mix ketchup on a large scale.

Now we get into the weird non-Newtonian fluids.

Rheopectic fluids get thicker in relation to the pressure being applied to them and the time that the pressure is being applied. The best example of a rheopectic fluid is cream. With enough time and pressure, cream becomes butter.

Thixotropic fluids are similar to pseudoplastics in that they get thinner as pressure is applied to them, but it’s also dependant on the time that the pressure is being applied. Things like cosmetics, asphalt and glue all fall into the thixotropic category.

It might seem like this is useless information, but it can actually be very useful, especially if you’re ever in a restaurant that still uses glass ketchup bottles. Simply remember that ketchup is a non-Newtonian pseudoplastic and will get thinner as more force is applied to it. Give that bottle a couple of good thumps, and you’ll be in French fry heaven.

Sources:

https://www.youtube.com/watch?v=RIUEZ3AhrVE

https://blog.craneengineering.net/what-are-newtonian-and-non-newtonian-fluids

https://www.philamixers.com/news/how-condiments-are-made/

The Science Behind Beer Kegs

BY MEGAN RAY NICHOLS

Beer kegs have been serving as the centerpiece of college parties and the backbone of many bars and taverns for decades. Typically available in a half or quarter barrel, the average keg can fill approximately 124 or 62 pints of beer, respectively. While it’s relatively simple to transport, store and use a keg around the home, there are some precautions to remember.

Typical Components of a Beer Keg

Despite the availability of different sizes, shapes and alternate materials, kegs are pretty standard around the world. As such, several components are found on nearly every keg.

  • The keg itself is typically made of stainless steel. While quarter barrels contain 7.75 gallons of liquid, the larger half barrel boasts 15.5. Smaller kegs, which are sometimes available, contain 5 gallons.
  • A coupler, sometimes referred to as a pump, is needed to withdraw beer out of the keg via the topmost valve.
  • Gas, either in the form of carbon dioxide or nitrogen, is used to help the beer flow smoother and quicker. The coupler or pump is often used, especially at parties, although it’s not as effective as gas.
  • Tubing is also required to transport the beer from the keg and into your cup. Commonly made of polyethylene or vinyl, some partygoers chill the tube for additional coldness.
  • If you’d rather forego the manual-powered party pump, your other option is to outfit your keg with a faucet. This ensures consistency between beer pours, which can help keep your party going all night long.

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The Principles of Building Indestructible Sand Castles

Introduction

If you had a formal education that touched even a little bit of composite materials in the course, you will immediately be able to recall what these amazing materials can do. For others, Composite materials, as the name suggests, are materials that are composed of two or more different kinds of materials.

In a simple case think of your body, which is, in a broad sense, a combination of skin material and bone material. These materials are designed to take advantage of the contrasting properties of, say two different materials. For simplicity’s sake, skin is soft and bone is hard. The bone gives body a solid structure, while the skin and muscle tissues enables this hard skeleton to make fluid movements – flex or bend – and still be together.

Individually the materials that make up a composite material are not very capable. But when they come together, composite materials can blow your mind. To appreciate how this simple coming together of two humble materials can create a super material, and to appreciate the mind blowing properties it can have, let us first look at what most of us have heard of – “Carbon Fiber”. We will get into the more mind bending aspect of composites after that.

Carbon Fiber Reinforced Polymers (CFRP)

Now carbon fiber itself isn’t a composite material. As the name suggests, it is a fiber of carbon. The fiber is composed of strands of carbon each of which are much thinner than a single human hair. Hundreds of these come together to form a thicker fiber. This fiber can be woven to make sheets or the carbon fiber itself can directly be used in a composite material.

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5 Things You Didn’t Know About Water Repellent Technology

Water repellent technology has advanced a lot since it was first introduced. Durable water repellent is a coating which is received by the products to make them water resistant and is made from nano structures. These nano structures are the result of the advancement in the modern chemicals and thus offer far more protection than any other thing. Here are some of the facts which makes explains how this new water repellent technology uses the concept of nano technology to help your car remain cleaner:

The Lotus Effect

The nano structures are byproducts of nanotechnology which are used to give protection to your car’s windows, windshields, rims and to the whole body. The main function of the hydrophobic coating is to act as water repellent agent making your car waterproof and increase the car’s auto wash cycles. The mechanism from which it was inspired is itself found in nature and therefore called as “Lotus effect”. This is named after lotus leaf which has self cleaning properties and insects such as butterflies and dragonflies also exhibit such properties.

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A Layman’s Guide to Photonic Crystals

The first time I heard the word “Photonic Crystal” in a seminar, I was stumped. So I decided to read about it, understand and then write about it to make it explain better to me, and you of course. Even though it is a whole graduate level class to explain, it does not hurt to quickly look at how Photonic crystals work. I have not taken the relevant graduate class. However, after reading this amazing answer on Quora, and from a range of other literature out there, I was able to make some good sense out of it. My idea was that at least by doing a little reading you get to throw around a fancy word like “photonic crystal”. Moreover, if someone decides to test you on what it means, you even explain it to them. These kind of examinations, where it is incumbent upon you to perform well, happen all the time, everywhere. That’s why it is important to learn. And well, then there’s that whole argument of expanding your mind to exercise your creative muscle by reading and listening carefully to things and people that are out of what you do.

Featured image credit: Flickr, Steven & Courtney Johnson & Horwitz (Picture)

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The Boat Puzzle

By Anupum Pant

I remember solving this problem when I was in the twelfth grade. However, I no longer remember how I did it. Nor do I remember the answer. The boat puzzle goes like this.

What if you are in a boat that’s floating in water (a small body of water) and have a rock in your hand. You choose to drop the rock into the water. The rock, as they all do, sink to the bottom. Did you just make the level of water rise, or make it drop, or did not change it at all. How? Try to answer and watch this for the explanation…

Making a Light Bulb was Never Easier

By Anupum Pant

Who’d have thought that making a real light bulb was so easy. Yes, the one with a filament that glows red hot due to the resistance. For this project the major things you’d need are, a power source (couple of D batteries), leads to connect them and a pencil lead as the filament. Go ahead and just put them together like this…

The Marvels of Samsung’s S Pen

By Anupum Pant

It’s amazing how far technology has come. The S pen you get with a Samsung note device has no battery in it, and yet it is powered because it can somehow communicate with the device. The communication is obvious because the pen has a button and if you press it, the phone knows.

So how does this work? What kind of sorcery is this.

The pen actually pulls energy wirelessly from the device itself with the help of electromagnetic waves. It is something like a device bremen-based designer dennis siegel built in the year 2012. He showed us how he could charge his batteries by harvesting the omnipresent electromagnetic energy. Although it used to take about 24 hours to charge a normal AA battery, now a similar tech is encapsulated in a tiny device, actually even thinner than a real pen!

Electromagnetic Harvester from Dennis Siegel on Vimeo.

Atoms Scream When They Die?

By Anupum Pant

At a state of the art fusion reactor at MIT, special machines heat up gasses at really high temperature, to about million degrees hotter than the sun’s surface. This makes them move around so fast that they are able to smash together and fuse. This right now doesn’t work as it should in theory. But when it does, it would be a great clean source of energy.

For now, what is interesting is a kind of noise atoms make just before they are about to fuse. The sound is like a shrieking baby. Here is what they sound like when they die…

Racist Sinks

By Anupum Pant

We’ve all seen automatic faucets and this is how they work. You put your hand, the water flows and stops automatically when the hand moves away. Or that is how they are supposed to work.

I came to US about 1 year back. Since then I’ve been to a number of restrooms which have automatic faucets in the sink. But every time I try to use them, these things fail me. I used to think it was due to the darker color of my skin, but then that was a little too far-fetched. I was pretty sure it was me who was doing something wrong in the foreign country. Probably things worked a little different here because we had the same things back in India too, they worked pretty well with my brown skin color.

And then I stumbled on this viral video which demonstrated the same thing. My first guess seems to be right. To confirm that I dug a little deeper.

Capture

This redditor seems to know why this happens. The sinks work because they shoot off an infrared beam outwards. When this beam is unobstructed, it is programmed to not send out water, or soap, like in this case. When these get obstructed by something that is close, the body reflects back some of the infrared back. That is how the faucet knows something is close.

Darker bodies however are known to be better absorbers. So, they absorb most of the infrared and send only a tiny amount of it back which is apparently not enough to trigger the faucet. The amount of reflected signal it receives before it can be triggered apparently can be tuned by doing trials. Probably since faucet companies in the US use white people for trials, they have a default trigger which requires a greater amount of reflected light, on an average. So it works for white skinned people but seems to fail people with darker color.

However, in India since these tests must be done with people who mostly have a slightly darker skin color, the faucets are probably programmed to work fine with that kind of skin color and for white skins too.

Strongest Magnets in the World

By Anupum Pant

Magnets are everywhere. They are in your headphones, phones, computers and what not? In fact, the whole planet, although a much weaker one, is a humongous magnet too. A simple bar magnet has a magnetic field that is about 200 times stronger than our planet’s magnetic field. And it only gets stronger from there.

Then there are neodymium magnets. They can get so powerful, they can destroy things by just getting attracted to each other.

Then come the electromagnets. Some of these kinds are used to handle metallic scrap. They can get magnetized to really high strengths and lift huge amounts of iron scrap and then when the current is switched off, they lose all of the magnetization. These scrap handling cranes can be 200 times more powerful than your average bar magnet.

But the world’s strongest magnets are found in the national magnet lab in Tallahassee, Florida. Besides being thousands of times more powerful than any other magnet around it in miles, these magnets are also built to be compact by utilizing essentially the same principle as the scrap handling magnets, with extremely dense winding which takes months to build.

One such beast is the strongest one there which can boast a field as strong as 45 Tesla. Trust me, that’s huge. Huge enough to pull you apart even if you are in the same building as this magnet while it is running. Being around the building probably gives you hallucinations. Don’t even think about having computers anywhere around it, their memories will get washed for ever.