# Sensei

Senior Members

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13

1. ## Anything Smaller Than Quarks and Leptons?

What is composition of bit? (in computer sense) We know that it can have value 0 or 1 (kinda like property of bit), and we know its address (kinda like position of bit). We can read bit, write bit, compare two bits, store it on disk, restore, group them to byte (8 bits), short (16 bits), long (32 bits) etc.etc. I am not saying that Universe is some kind of database or so. Universe is "alive". Particles interact constantly. But as you can see in above example, not everything has to be made of infinitely smaller things. Bit is unbreakable. It's fundamental.
2. ## Ideas for a side game to play on SFN.

A. Erwin Schrödinger B. Marie Skłodowska-Curie

18. ## Is Coulumb's Law, Symmetrical????

And we can see traces leaved by them in Cloud Chamber. Long thin traces are from beta particles (electron or positron). Short thick traces are from alpha particles. The more kinetic energy has particle, the longer trace.
19. ## Is Coulumb's Law, Symmetrical????

No. Just electron. Aluminum atom has 49218 times more mass than electron. Copper atom has 117667 times more mass than electron. Gold atom has 359109 times more mass than electron. When electron flows through conductor it sometimes hits atom, losing a bit of its kinetic energy, and heating atom, which is receiving electron's kinetic energy. The less this happens (lower resistance), the better conductor. If we have atom which lacks electron (ion+), and atom which has more electrons (ion-), the one that has more can give electron to the one which lack it. In batteries that have 1400 mAh on negative electrode we have 5000 Coulombs = 5000*6.24*10^18 = 3.12*10^22 electrons, and on positive electrode there are positive ions in the same quantity, which lacks electrons. After closing circuit electrons flow from negative electrode to positive electrode. Positive ions are attracting electrons. Each electron will have kinetic energy that corresponds to voltage difference. f.e. if voltage is 1 V, single electron will have 1 eV kinetic energy (electron volt unit). if voltage is 3.5 V, electron will have 3.5 eV kinetic energy. E=h*c/wavelength so wavelength = h*c/E = 4.135667*10^-15 * 299792458 / 3.5 = 354 nm UV LED have voltage drop 3.2-3.5 V (a bit is probably lost). So they emit photons with energies 3.2-3.5 eV, which correspond to wavelengths 387 nm .. 354 nm. Photon in ultraviolet spectrum. Where did you get such conclusions? I said "If you have single electron, charge Q will be -1.602*10^-19 C. If you have single proton, charge Q will be +1.602*10^-19 C." One has positive, other negative.
20. ## Help my understand why my cell phone charger current quantification failed!

2.1 A * 3600s = 7560 C. 7560 C / 2.1 C/s = 3600 s = 1 hour to charge to full with 2.1 A current. Is it plausible estimated time (assuming you don't play game at the same time ) ? Amper hour unit Ah is simply 3600 Coulombs. 1 Coulomb is 6.24*10^18 electrons. That's no surprise. After all it's more electrons per second. 1 A is 6.24*10^18 electrons, 2.1 A is 1.31*10^19 electrons per second. Apparently these games are using more energy than charger is able to provide. I guess so, heavy 3d. Do you have app showing cpu/gpu percentage usage with history.. ? Perhaps some application running all the time in background that's eating energy? Also loading a lot data to memory might have such effect. Typical computer random access memory must be refreshed periodically by current to sustain content. I had one Nokia 10 years ago that ate power like crazy when it was full of data. After deleting everything it could work several times longer. Current ebook technology is using screens that use power only while changing display. Games changes display even 30 FPS. Not sure whether such screens are used by some mobile phone. Might be highly model dependent.
21. ## Is Coulumb's Law, Symmetrical????

Q in Coulombs [C] is charge. It's kinda like quantity of particles. 1 C = 6.24*10^18 electrons. If you have single electron, charge Q will be -1.602*10^-19 C. If you have single proton, charge Q will be +1.602*10^-19 C. Electrons and electrons repel. Protons and protons repel. Electrons and protons attract. So, if you have Q1=-1 C and Q2=-1 C, after multiplication negative by negative, we will receive positive value. F=k*-1 C * -1 C / r^2 = k*1*1/r^2 If Q1=+1 C and Q2=+1 C F=k*1*1/r^2 effect will be the same. You can see how it works using electroscope. http://en.wikipedia.org/wiki/Electroscope "leafs" are free to move. The higher quantity of electrons will gather on them, the further leafs will be from each other.
22. ## Help my understand why my cell phone charger current quantification failed!

Imagine you have discharged cell phone battery to null. How long it takes you to charge it to 100% full again? If your cell phone battery has 1000 mAh, and loading current would be 2.1 A, it would charge to full in just 500 seconds = 8 min 20 sec (let's assume no loses). With 0.2 A, it would be 80 mins+. Mine cell phone battery has 3.7 V and 3.7 Wh on its back. Which is 1000 mAh. How could you do it? Typical voltage meter has as largest resistance as possible, usually a few mega ohms AFAIK. And ampere meter has the smallest resistance as possible. http://www.allaboutcircuits.com/vol_1/chpt_8/5.html

24. ## Wiring a DC motor

I plugged DC motor (from old cassette Walkman or so) to 5.5 V 4 AA batteries that I had at hand. Without anything Ampere meter is showing 2.4 A. With DC motor Ampere meter is showing 0.210 A, voltage drop on DC motor is 1.5 V (4 V remaining). With DC motor and 210 ohm resistor, 0 A, and motor doesn't want to run. With DC motor and 4.3 ohm resistor, 0.19 A, voltage drop 1.5 V. Motor runs but slightly slower than without resistor.
25. ## logarithm

log10 ( 10 ) = 1, because 10^1=10 log10 ( 100 ) = 2, because 10^2=100 log10 ( 1000 ) = 3, because 10^3=1000 etc. log2 ( 2 ) = 1, because 2^1=2 log2 ( 16 ) = 4, because 2^4=16 log2 ( 256 ) = 8, because 2^8=256 etc. Common bases: ln(x) = loge(x), base is e log(x) = log10(x), base is 10 In your example, if base is 5, then log5(125)=3
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