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Biology; Chemistry; Physics: Post your doubts here!

Discussion in 'Cambridge O Levels' started by scouserlfc, Sep 13, 2011.

  1. scouserlfc

    scouserlfc

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    Assalam-o-Allaikum and Hi everyone ,
    hope u all are doin great !

    Well as the topic says help for chemistry :D biology :D and Physics :D is available here that means that u can ask any mind blowing question or ask any question regarding a particular topic or ask abt any questions from Past paper or any of your text books. (y) (y)

    I made this topic so that people dont make many posts asking abt bio,physics or chemistry individually but they can post their reply here where it can be answered with ease and the members wont have to go searching for topics to help! :D !

    So what are u waiting for now write ur questions here !
    THANKS and Bye or Allah Hafiz ! (y);)
     
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  3. VelaneDeBeaute

    VelaneDeBeaute

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    Re: Biology,Chemistry & Physics Help Available Here !

    @scouserlfc .. great idea !! :Yahoo!:
    However Mods, sticky this topic, would you ? :)
     
  4. Nibz

    Nibz XPC Global Moderator Staff Member

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    Re: Biology,Chemistry & Physics Help Available Here !

    Wassalam!
    Topic made sticky.
     
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  5. Silent Hunter

    Silent Hunter

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    Re: Biology,Chemistry & Physics Help Available Here !

    nice thread..........i will try ma best to answer the questions i can :)
     
  6. scouserlfc

    scouserlfc

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    Re: Biology,Chemistry & Physics Help Available Here !

    thanks for the positive response ! i appreciate it ! :D

    anyways anyone has any questions we will be happy to solve them !
     
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  7. Nibz

    Nibz XPC Global Moderator Staff Member

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    Re: Biology,Chemistry & Physics Help Available Here !

    Here is my question:
    If a mass-less box travels at 7.293 x 10^0 microdoodles, what time will it be in Karachi when Altaf Hussain next sings the song 'Parday main rehney doh'? :p
     
  8. VelaneDeBeaute

    VelaneDeBeaute

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    Re: Biology,Chemistry & Physics Help Available Here !

    ^^ Extremely thoughtful !! :eek:
     
  9. SalmanPakRocks

    SalmanPakRocks XPC Moderator Staff Member

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    Re: Biology,Chemistry & Physics Help Available Here !

    Can some one explain to me what is the difference between these and the define them
    1)Potential Difference
    2)E.M.F
    3)Current
    4)Volts
    If Currents and Volts are same then please Pardon me, Actually my teacher doesn't explain us anything and just gives us questions which are totally out of my mind. Worst in Physics
     
  10. multixamza01

    multixamza01

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    Re: Biology,Chemistry & Physics Help Available Here !

    E.M.F :
    This is the ''electromotive force''. It is any form of energy converted to electrical energy.

    Potential Difference :
    It exits between two points. For example point A has 3V and point B has 5V. So we say that a potential difference of 2V is established between the two points.

    Current :
    The measure of the rate of follow of charges through a given cross section of a conductor.

    Volts :
    The amount of electrical energy provided by a source.

    These are not the exact definitions , but are just for explaining.
     
  11. multixamza01

    multixamza01

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    Re: Biology,Chemistry & Physics Help Available Here !

    Need help. What is the chemical formula of potassium sulfate? is it K2SO4 or KSO2?
     
  12. VelaneDeBeaute

    VelaneDeBeaute

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    Re: Biology,Chemistry & Physics Help Available Here !

    Potassium = k ^ +1
    Sulphate = SO4 ^ -2
    Potassium Sulphate K2SO4
     
  13. scouserlfc

    scouserlfc

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    Re: Biology,Chemistry & Physics Help Available Here !

    wow i was away and we had two questions and one very thought provoking question which i cant even answer such a pity Mr Nibz maybe u give the answer ur self since its not in our syllabus :p :p :p :p !

    Also for salman dude take it easy and dont fret Current elect is a very vast and one of the big topics in our physics so it will take time read the book u have and yeah u can surely ask us the problems !!!
     
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  14. SalmanPakRocks

    SalmanPakRocks XPC Moderator Staff Member

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    Re: Biology,Chemistry & Physics Help Available Here !

    Never Change the Formula! Only Valencies are cross multiplyed so the formula will be as Ghalya stated !!
     
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  15. multixamza01

    multixamza01

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    Re: Biology,Chemistry & Physics Help Available Here !

    ^^^ Yea , i was thinking wrong when i asked the question.
     
  16. boxfire1995

    boxfire1995

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    Re: Biology,Chemistry & Physics Help Available Here !

    guys, can anyone explain to the the manometer and barometer? i do know it, but what will happen if we use a liquid lighter than mercury? or if we sink the tube of manometer in the reservoir? will the height be the same of mercury?
     
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  17. scouserlfc

    scouserlfc

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    Re: Biology,Chemistry & Physics Help Available Here !

    barometer is used for calculating liquid pressure while manometer the gas pressure now what do u mean by sinking the tube of manometer !

    Also if u use a liquid lighter then mercury then the height of the liquid will be more depending on the density of mercury and that liquid !
     
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  18. VelaneDeBeaute

    VelaneDeBeaute

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    Re: Biology,Chemistry & Physics Help Available Here !

    @boxfire1995 what actually didn't you get about barometers and manometers ?? The way they work ?? :)
    If the liquid is lighter, it will be more sensitive to the temperature changes. As in, it will rise more in length for comparatively small changes in pressure !!

    The main thing to remember about this question is that the atmospheric pressure pushes the level of mercury up exactly 760mm. This is whether you pull the tube up 10 mm or sink it down 5 mm or tilt it at an angle.
    Pressure in a liquid is p(row)gh, it does not depend on the shape or size of the container, only the height of the liquid, density of the liquid and gravitational force affects the pressure. Since the pressure/density/gravitational force is constant, hence the height of the mercury column remains the same.

    However, you may also check these websites !!
    Liquid Barometer
    The Aneroid Barometer
    Manometers

    Hope it helps :)
     
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  19. multixamza01

    multixamza01

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    Re: Biology,Chemistry & Physics Help Available Here !

    Your question is wrong. Barometer measures liquid pressure. Manometer measures gas pressure. You should learn it. It's confusing , and would cost you later on , so get it straight. Manometer measures gas pressure and barometer measures liquid pressure.

    Barometer :
    Refer to the book for the diagram. Uses the relation :
    Pressure in liquid = Density of liquid x gravitational field strength x height of liquid coloumn.

    So in other words if any one of the the three varies , the liquid pressure would vary accordingly. For example if a denser liquid is used , the pressure will increase. If the length is increased the pressure increases. But the gravitational field strength will not change as it is the same everywhere on the planet , but if it were to change , yes the pressure would increase.


    Manometer :
    Refer to book for diagram. ( it is advised you keep the diagram with you while reading this)
    Now as you can see a manometer is a U shaped tube. If you pour liquid into it , the liquid levels reach the same height of both sides. Now to measure the gas pressure , you attach a gas supply to one end. If the gas pressure is more then atmospheric pressure ,then the liquid level will fall in the attached tube. Accordingly the level will rise in the other tube. The level that falls and the level that rises are equal. i.e if the level that has fallen is 2 cm , then the level that rose is also 2 cm. The gas pressure is calculated by adding both levels.

    Pressure of gas = Level of liquid that falls + Level of liquid that rises.


    Hope this helped.
     
  20. scouserlfc

    scouserlfc

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    Re: Biology,Chemistry & Physics Help Available Here !

    yeah multimax is 100% right did u even read the book man if not try it ull get it in one go,so now u cant say that the manometer can be sunk into the reservoir its strange what u mean ! 8)
     
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  21. boxfire1995

    boxfire1995

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    Re: Biology,Chemistry & Physics Help Available Here !

    sorry about mixing it up.... i was in a hurry.... and yes. i did get but i was a little stuck on a 87 past paper question.... so no biggie. =) thanx btw.
     
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