physics people, help me?!
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hey, what does a capacitor exactly do huh? I do know it store charges and stuffs like that? But what's its practical application? Im weak in the chapter of DC circuits and Current of electricity. Hee heh
How bout also the chapter of Ideal gases,
the number of moles
number of molecules
molecular mass
Im pretty confused by this. I think they also have the same symbol. N(a), n, M(m) or whatever hell that is -
ideal gasOriginally posted by Qex:hey, what does a capacitor exactly do huh? I do know it store charges and stuffs like that? But what's its practical application? Im weak in the chapter of DC circuits and Current of electricity. Hee heh
How bout also the chapter of Ideal gases,
the number of moles
number of molecules
molecular mass
Im pretty confused by this. I think they also have the same symbol. N(a), n, M(m) or whatever hell that is
low presssure high tem is ideal gas
all gases extraplorate at -273.15k
all motion cease.
they all have mininium ke.
in a sense they are not hitting the wall. -
capacitor:
charges go in, capacitor will store, until cannot store anymore, then charges cannot go in anymore, so become open circuit. -
Ideal gases will follow this formula:
PV = nRT
where
P is pressure
V is vol
n is no. of moles
R is a constant
and T is temp in K
n = mass / molecular mass
eg: if you have 16g of Oxygen gas then..
n = 16/32 = 0.5 moles
So to continue, in a closed environment, ie n,R and V are constant.
hence Pressure is proportional to the temp..
Normal gases tend to be like ideal gases when at low temp and low pressure..
I hope im right so far.
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*faints*
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1 mole of molecules/atoms contains 6 x 10^23 particle.
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low pressure high temp la..Originally posted by Orange_Monster:Ideal gases will follow this formula:
PV = nRT
where
P is pressure
V is vol
n is no. of moles
R is a constant
and T is temp in K
n = mass / molecular mass
eg: if you have 16g of Oxygen gas then..
n = 16/32 = 0.5 moles
So to continue, in a closed environment, ie n,R and V are constant.
hence Pressure is proportional to the temp..
Normal gases tend to be like ideal gases when at low temp and low pressure..
I hope im right so far. -
capacitors can store electrical charges.
in a ac-dc convertor, it is used to regulate the voltage output of a four-diode bridge to give a relatively smooth dc output. -
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it is used to filter off reactive power aka power factor correction.
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Capacitor
I used to not know how a capacitor works last time until one of my friend used this analogy.
He asked me to picture this spherical container with a piece of plastic sheet in the middle. When the container is filled up with water, the plastic is straight and not bent.
Now, imagine is water is being pumped from one half to the other through an external tube. Due to higher water pressure on one side, the plastic sheet will bend towards the other. This continues as long as the water is being pumped continuously from one half to the other through the external tube.
However, when the pumping stops, the water from the side with higher pressure will flow back to the side with lower pressure, hence causing the plastic sheet to return to its original shape.
Similarly, a capacitor works in the same way. It stores charge when there is an external source of electromotive force (emf). It keeps storing the charge until there is no external emf and then it will start to release the stored charge in it, analogous to the above example. That's why it is used to smooth out a current in a simple 4 diode full-wave rectifier (from AC to DC). This is because when there is current in the circuit, the capacitor stores the charge. When the current stops, the charge in the capacitor gets released to the circuit and hence help to smooth out any sudden changes in the current. (BTW current = charge per unit time).
Ideal Gas
Depending on your level, I will assume that you are around A level/Diploma to Uni Year 1 or 2.
The Ideal Gas Equation: pV = nRT
p = pressure in Pascals (or newtons per metre square)
V = volume
n = number of moles
R = molar gas constant (8.31 J per mol per Kelvin)
T = temperature in Kelvins (To convert from Celsius to Kelvins just addid 273.15)
You may also come across another form of the Ideal Gas equation: pV = NkT.
The only difference is that Nk is in the place of nR. Numerically, they're equivalent but they stand for different things.
k = Boltzmann constant.
N = Number of particles and it is = n x Avogadro's Number = n x 6.0 x 10^23
From now on I shall use the symbole Na for Avogadro's Number. (it is usually written big N with a subscript a)
So manipulating, you will realise that the Boltzmann constant = Molar gas constant divided by Avodagro's Number (i.e. k = R / Na)
Do the manipulation and you will realise that Nk = nR.
Now onto molar mass and the number of moles.
In chemical terms, there are a few symbols. We have encountered N and n. Let's look at m and M.
M = Relative molecular mass/Molar mass
m = actual mass.
So how are they related? M = the mass of a substance if there is 1 mole of that substance, so by this relation, m = M x n (see the mass of something is the number of moles multiplied by the molar mass. An analogy is finding the price of veggies. We take the price of 1 kg of veggies multiplied by the number of kg of veggies to get its price.)
From here, n x M = m, so n = m/M. Sub this relation back into the ideal gas equation, pV = (m/M)RT. That's another form of your ideal gas equation if you are just given the mass of the gas and asked to find the molar mass of the gas.
Hope it helps you.
Physical chemistry or Thermal Physics is just this equation + another 2 to 3 more. More practice and you should find them easy to grasp in no time. -
hey thanks teraexa!!
love you lots
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capacitors make sure my circuit dun go kaboom
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BTW you sound like you are studying J2 topics.
DC Circuits and Current of Electricity smells a lot like J2 topics.
If you are J2, my advice is that you do not bother about capacitors. They are not in the current H2 syllabus anyway. You just need to know your potentiometer concept well.
For the ideal gas equation, if you are J2, just heck care about pV = NkT cos that's in neither H2 Physics nor H2 Chemistry syllabus. Just get your pV = nRT.
I speak from experience as I am also J2.
LOL.
BTW to make sure my circuits dun go kaboom, I don't rely on capacitors. I use fuses. I think fuses are safer than capacitors. -
pv=NkT also impt..some question u nid use this formula to solve...eg when they give u N u juz sub N into can le..dun nid find mole (n)Originally posted by teraexa:BTW you sound like you are studying J2 topics.
DC Circuits and Current of Electricity smells a lot like J2 topics.
If you are J2, my advice is that you do not bother about capacitors. They are not in the current H2 syllabus anyway. You just need to know your potentiometer concept well.
For the ideal gas equation, if you are J2, just heck care about pV = NkT cos that's in neither H2 Physics nor H2 Chemistry syllabus. Just get your pV = nRT.
I speak from experience as I am also J2.
LOL.
BTW to make sure my circuits dun go kaboom, I don't rely on capacitors. I use fuses. I think fuses are safer than capacitors.
ai yo...juz memorise 1 more nia...wun die larhs