In the last blog you must have met with our “peaceful” Dragon. She loves cooking but she is bothered all the time by the failing appliances of her kitchen that I have to mend always (poor me) and I let her know of the kitchen physics that keeps me safe:D.
Me: "Good Morning Dragon! Is everything okay?"
Dragon: “Yup”
Me: “It seems you are in a hurry. What’s up?”
Dragon: “I am late and I’ll have to reach office soon and today everything was so messed up plus I suffered an electric shock”
Me: “Aw, why? What messed up?”
Dragon: “My water heater, I shouldn’t have used this old wicked thing.”
Me: “Okay I’ll see to it but why are you stirring your nonstick pan so vigorously with steel spoon, it might damage it.”
Dragon: “Why non stick cookware should not be stirred with steel spoons?”
Me: “See Dragon, Nonstick cookware is made of aluminum and related alloy very much like ordinary cookware, but what makes them different is the special coating of Teflon on its surface. Teflon is a polymer and not metal which is very stable towards high temperature and it gives the cookware the property of non stickiness.
If nonstick cookware be stirred with steel spoons, steel being harder than Teflon puts scratches on it and with time the Teflon coating wears away thus the “non stick” property of the nonstick goes and it becomes useless."
Dragon: "Um okay, but how is hardness related to the scratches made?"
Me: "Good question Dragon; a hard substance can produce scratches on a soft substance. Let us for example take the instance of our finger nails and wax…can you tell me which one is harder?"
Dragon: “Obviously our finger nail; mine is harder than yours though.”
Me: "Have you ever noticed Dragon that our fingernails can mark scratches on wax? Well, can wax mark scratches on our fingernails? No, because harder scratches softer. In fact physics measures hardness of a substance in comparison with another on the basis of scratches made by one on the other and a scale for measuring hardness of minerals exists by the name Mohs scale. The scale is arranged in ascending order of hardness comprising 1-10 indexes. Softer ones like Talc has a position 1 and the hardest ones like diamonds have 10 on Mohs scale. The scale is simple: the higher members on the scale can mark scratches on the lower ones."Dragon: “Is diamond harder than steel?”
Me: “Yes diamond is way harder than steel is, it’s harder than glass too, and that is why diamond marks scratches on glass”
Dragon: “Don’t make me crazy, glass can’t be harder than steel I can prove it just now…”
Me: “Oh no Dragon! Please do not prove it now, let me explain… What we see or believe with common sense may be wrong; physics says glass is harder than steel because glass stands at 6 whereas steel is only at 4.5 on Mohs scale. We are sometimes tempted to assume glass softer than steel because we are misled by its high brittleness in contrast with steel’s high elasticity. Steel is obviously stronger than glass but glass is harder than steel.
Seems like a paradox? It would be easily resolved if we understand the following rule.
That is in physics “strong” refers to a substance’s high elasticity i.e. its ability to restore to its original state after getting deformed by a force whereas “hard” refers to a substance's scratching ability or its molecular/atomic bond strength.”
Dragon: “Good! I have learnt a new stuff and I’m happy coz I have got a pair of diamond rings”
Then I started inspecting her water heater and found that it had no grounding with it.
Me: “Hey! Dragon throw away your dangerous water heater, it may prove fatal someday.”
Dragon: “Yes I am going to put it right out of my doors but can you tell me what the problem with it is?”
Me: “It has got no grounding connection.”
Dragon: “What is grounding (earthing)? Is it necessary? If so why?"
Me: “Grounding is a connection of the exposed metal parts of electric appliances with the earth. Have you ever noticed a 3-pin electric plug? The topmost pin is the grounding pin.
Yes Dragon, grounding is very much necessary and it can be life saving at times because it prevents contacts with hazardous voltages that one may come across in case of insulation failure and short circuits by transferring the current directly to earth instead of making it travel through the person's body.
Moreover, grounding protects electronic equipments like computers etc from static electricity and also from the danger of lightning bolt using lightning conductors.
So Dragon, before buying any electrical equipment check whether it has got adequate ground connectivity (a 3-pin plug means it has ground connectivity)”
Dragon: “O my God! I will burn those cheap factories that make non standard devices.”
Me: “That’s like a good Dragon!”:D
Dragon: “Now I am too afraid to buy electric devices but I have bought this new oven last week, it is some magic because it does not have any heating filament nor it has got any microwave facility. The dealer told me it is a techie marvel called Induction Oven. Can you tell me whether it is safe and how it works?”
Me: “Induction ovens aren’t a technological marvel compared to microwave ovens and I can see it is quite safe to use because it has got a good ground connection too. But it’s working although simple needs a deeper understanding on a branch of physics called electrodynamics.
Let me explain how it works. See it has been found that if a magnet be moved very fast in to and fro motion near a metal plate it generates a circling current in the plate, this is known as eddy current. Now if this eddy current is allowed flow for sometime, heat is developed in the metal plate. As because it is impossible to move a magnet such fast; a similar effect of changing magnetic field is generated by letting AC current flow through a copper coil which is placed inside the oven. Eddy currents get developed in metallic cooking utensils (favorably ferromagnetic) placed above the induction oven and gets heated. 
But Dragon you have taken a very good decision for cooking with induction oven. It is one of the most efficient cooking methods available and transfers nearly 84% of the energy to the food compared with 40% for cooking gas and 71% for conventional electrical heaters. So it is good for environment”
Dragon: “Physics is interesting I used to hate it in my college days but I have noticed it has just leaped into my kitchen and poor me I don’t know anything.”
Me: “Aw, who says you don’t know anything? See you have learnt and understood so many things and we all must learn from someone or the other, don’t we? Cheer up Dragon a smile on your face worth a lot. (Not the Dragonic grin though :D)”
Dragon’s refrigerator was not working well; it was too much noisy and was not cooling properly. She asked me to inspect it and I found problem with the compressor and some turns of the compressor motor that had burnt.
Me: “You will have to take it to the service centre; the compressor motor has worn out.”
Dragon: “I don’t like failing things, the refrigerator is of good quality still and is still under warranty period.”
Me: “Refrigerator warranty generally comes under two criteria warranty on the refrigerator and its compressor. Both may have different extent of warranties too.”
Dragon: “May be I have got both, but can you tell me how a refrigerator work… is it a device to produce ice that cools things fast?”
Me: “If refrigerator cools by producing ice then the obvious question is how it produces ice? Refrigerator doesn’t cool by producing ice but cools by evaporation and adiabatic expansion of a suitable gas called refrigerant.”
Dragon: “How come evaporation cools?”
Me: “Okay just switch on the table fan and keep your hand in the direction of the wind, note what you feel, then wet your hand with water and then repeat the same, did u feel any difference?”
Dragon: “Hey what I feel is obvious, my hand is dry and I feel colder air after wetting my hand.”
Me: “Exactly! But the air hasn’t cooled down as you know so, what did actually happen after you have wetted the hand? See the water in your wet hand has evaporated under the current of air and has taken the heat from your hand with the water vapors. With the decrease of heat on your hand you are feeling cold. Now we know that water is not a very volatile substance but if we repeat the experiment taking a very volatile substance like alcohol etc the fall in temperature is quite pronounced. It is because a volatile substance evaporates quickly and cools faster.”
Dragon: “I have never thought that way; a simple evaporation drives a refrigerator! Can you tell in details? Okay but what was the other Greek term? Yes adiabatic expansion. What is that?”
Me: “Many types of refrigerators exists, the one at your home is a vapor compression type refrigerator. Here, a suitable gas for refrigeration is chosen having properties such as easily liquefiable, high, latent heat of vaporization, low specific vapor volume etc. The gas is kept liquid under pressure and is passed in through the evaporator i.e. refrigerator coils (metal pipes) where it is allowed to evaporate by expansion inside the pipes. This reduces the temperature by drawing the heat from the refrigerator by two processes viz. adiabatic expansion and temperature fall due to evaporation, producing cooling effect in the refrigerator. After evaporation, the gas is led to through pipes to the compressor pump where it is liquefied under pressure and it condenses into liquid in the condenser. This liquefaction by the compressor gives away heat and this heat is discarded from the back of the refrigerator. The compressor acts like the heart of such type of refrigerators and is driven by an electric motor, which has worn out in your case.”
Thermos Flask is a good example
of Adiabatic System
Me: “Now adiabatic expansion and adiabatic compression are very important states in physics. Dragon, have you ever noticed that cycle or car tyres get heated when inflated? This is an example of adiabatic compression. When a process is carried out in an environment (known as system) such that no heat can enter nor leave it, it is called adiabatic process. As adiabatic compression increases the temperature of the system an adiabatic expansion leads to fall in the temperature of the system. In refrigerators expansion of the gas through the expansion valve is an example of adiabatic expansion and it leads to fall in temperature.”Me: “So Dragon you have learnt a lot on cooling, haven’t you?”
Dragon: “Yuppers! I’ve learnt a lot. So wonderful is the world of physics; I wish I were a physicist, so many things are there to learn that too in my kitchen itself.”
Me: “Now I have a question Dragon. How do you manage to vomit fire? I know no laws that let you do this. Is it another adiabatic compression?”
I have not realized what blunder I’ve committed; she is a dragon means she is not to be trifled with. I’ve dared to question the mechanism of fire vomit and I’ll have to pay for my sins.
At once she rose up…shifted her shape…Swore up high in the air telling me “I’ll show you how” I am running for my life …save my soul…see you all next week.
1 comments:
Hi, John here. If you’re looking online for a solution to power your home for free, I’m happy you’ve found my website. The results of my recent research will likely save you money and a lot of frustration. If you’re not one of my regular subscribers, let me tell you a little about myself and then you will see for yourself why you should consider trying a Free Energy Generator System to produce ALL of your Home Energy.
Post a Comment