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gonelli

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Posts posted by gonelli

  1. Is there a precise voltage that does NOT dissociate H2 and O2 and leave the water unchanged and only remove the dissolved salt ions ?

    Miguel

     

    If you apply a voltage that is less than around 2.60 V then theoretically you shouldn't get H2 or O2 being produced at the electrodes. But I'm not sure about what will happen with the movement of the ions.

  2. If I move the magnet at 20-30m/s I want to get at least a few volts.

    Do you realise that 20 to 30m/s is 72 to 108km/h? I would think that is a little fast to do by hand.

     

    How can I calculate the maximum potential generated? I don't know how to calculate the field, all I have is the magnet but how do I measure its field in Tesla or Gauss?

     

    Well, you can use EMF(peak) = NBAw to work out the peak voltage produced. Where, N = number of turn of wire (coils)

    B = magnetic field strength in Tesla

    A = total internal area of the coils

    w (which is meant to be a small omega) = angular momentum [ = 2(pi)*frequency]

     

    But as you said you don't know the field strength...so, you could use F = BIl to work out an approximate B (field strength), from known force, current and length of wire. This might explain what to do.

  3. The factors that determine if a fuel cell is more efficient, or better for the environment, compared to something else are based upon things like what kind of fuel cell it is, what reactants are used to run it, and where those reactants have come from.

     

    You probably should have a read about fuel cells, that will make the argument between you and your friend more understandable.

  4. I was under the imperssion that crops are genetically engineered to withstand diseases that are proving troublesome.

     

    Not all instances of genetic engineering, that I've read about, were aimed at disease protection.

     

    Some modifications were designed for plants/crops to be able to survive frost or grow in very cold conditions, while the original plant would have failed in such circumstances. And then there's the possibly over-ambitious ideas of some geneticists to modify vegetables to taste like chocolate, etc.

  5. Well, lets assume a mirror can reflect infrared light.

     

    A mirrow reflects light that is shined upon it, so what goes in will be pretty much the same as what comes back out. If you can't see the infrared light going in, will you be able to see the infrared light coming out?

  6. You have to keep in mind that the melting temperature of a substance is dependent on factors such as pressure. At the core of the Earth, I can only imagine that there is a fairly significant amount of pressure against the very hot ball of metal.

     

    As for its properties - I have no idea. I'm not well versed in the theory of what ever topic the centre of the Earth would fall under.

     

    _____________________________________________________________________________________________

     

    Ahhh, beaten to the punch

  7. For example, a fifth chord (for example A 27.50 Hz --> E 41.20 Hz) sounds pleasant to the ear. Is there anything like a fifth chord for colours ?

     

    I looked at 450 nm and 675 nm (which have the same frequency ratio - 1.5 - corresponding to a fifth)

    McCrunchy

     

    Just thought I point out that when you looked at the ratio in coloured light you were comparing wavelengths (450 nm and 675 nm) not frequencies like in sound.

     

    Anyway, I also agree with swansont. But, it was an interesting idea.

  8. ...they've actually gone so far as to practically ban an element (iodine) in the US (woop, over here we can but 10kg of iodine and nobody cares :))

     

    I hope they haven't stopped using iodine in foods/salts, because that would mean a whole lot more people walking around with goitres!

  9. I recall a maths lecturer taking a problem similar to this and going through it in front of the class. I'm pretty sure the initial premise of "a=b" was the problem, and wouldn't that suggest why you end up with a situation of the positive and negative answer both being equal to the same value?

  10. Ahhh... VCE. It wasn't so long ago that I did that experiment. By the way, I thought SAC stood for "School Assessed Coursework"?

     

    Anyway, you look to be pretty much on the right track. However, with the ground liver sample there may be another reason for increased reaction (it is a concept that the course wants you to link back to, so look through your notes).

    As for the detergent... when you blow bubbles into a glass of water, how long do they last for? Think about that.

  11. Uhhh... I don't think you will be able to perform the electrolysis of NaCl.

     

    ---------------------------------------------------------------------------------------------

     

    This just occurred to me, are you referring to the electrolysis of water in a NaCl solution? Where you will end up getting H[math]_{2}[/math] and O[math]_{2}[/math]?

  12. A salt water + small amount of electricity combo should corrode the steel quite well. That combo is the bane of coastal boat owners...

     

    That combo is essentially what you would need for electrolysis. Setting it up with the steel as the anode would allow for fairly fast rusting, as long as the current isn't too low. Around 1 - 2A would be alright, I think.

     

    Only thing is you need to make sure the Fe2+ ions come in contact with oxygen, so if the area to be rusted is just at the surface of the salt water it would be better.

  13. If ozone is the chemical in our atmoshere that traps heat from the sun, why then they're saying ozone is also pollutant harmful to humans???

     

    Ozone doesn't trap heat from the sun, rather it filters light from the sun:

     

    From Wikipedia "Ground-level ozone is an air pollutant with harmful effects on the respiratory systems of animals. Ozone in the upper atmosphere filters potentially damaging ultraviolet light from reaching the Earth's surface."

     

    It's a chemical that is beneficial for us being safe in the sun, but when at a great distance away from us. Seems to fit that old saying, "too much of a good thing can be bad for you".

  14. I recall reading that breathing through your nose allowed air to be filtered. Dust particles and other things being removed by the hair in the nose meant less irritation to the lungs/throat. And, as the air moved through the nose passage (bad terminology there) it would be heated up, I guess to make it more "human body friendly".

  15. I'm not an expert on the topic, but my understanding of the universe expanding is that matter is becoming more spread out, not being streched.

     

    Similar to how gas being stored in a container will expand if the volume of the container increases. The physical size of the gas particles will not change, but the average distance between them does increase.

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