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Physics: Post your doubts here!

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Hi,

Do u have alll the past papers for 2012(June and Nov) PHYSICS? I can't find some 2012 on this site.
Also I need further maths (all modules including mechanics) and Maths and CHEMISTRY.
 
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how do you find the time interval using the callibrated time base of a cro?
 
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Asalam-o-Alaikum!
could you please answer this question for me and give the working out as well?? nd asap!
A certain organ pipe, closed at one end, can resonate at consecutive frequencies of 640 Hz, 896 Hz and 1152 Hz. Deduce its fundamental frequency.
 
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ScreenShot2013-01-26at111205AM.png
In this question, logically the answer I think (and also my teacher said this) that it would be A because the cell needs to be varied (in order to increase voltage, current and thus allow the diode to conduct) so B and C are wrong. Then it has to be A because D isn't forward-biased i.e. current travels from positive terminal and is blocked by the diode, so it HAS to be A but the mark scheme says that the answer is D for some reason, can anyone please care to explain?
 
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can sum1 plz ans ASAP
count the 1cm boxes for the wave and multiply with the caliberation. be careful to convert the time where needed.
if u don't get it then ask again and i'll do what i can to help :) gud luk :)
 
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View attachment 20886
In this question, logically the answer I think (and also my teacher said this) that it would be A because the cell needs to be varied (in order to increase voltage, current and thus allow the diode to conduct) so B and C are wrong. Then it has to be A because D isn't forward-biased i.e. current travels from positive terminal and is blocked by the diode, so it HAS to be A but the mark scheme says that the answer is D for some reason, can anyone please care to explain?
maybe bcuz the question says "when it JUST conducts" then if it is working then it would record the voltage of the passing of current and we can't record it for the instant it begins to conduct... by reversing the diode it blocks the current after it reaches the diode and that current is measured.
 
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maybe bcuz the question says "when it JUST conducts" then if it is working then it would record the voltage of the passing of current and we can't record it for the instant it begins to conduct... by reversing the diode it blocks the current after it reaches the diode and that current is measured.
I don't understand, what do you mean by 'if it's working then it would record the voltage of the passing of current...'? Can you explain further please?
 
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maybe bcuz the question says "when it JUST conducts" then if it is working then it would record the voltage of the passing of current and we can't record it for the instant it begins to conduct... by reversing the diode it blocks the current after it reaches the diode and that current is measured.
Do you mean that in D, the current would be blocked except when the emf is high enough, at THAT point the current will start passing and the reading on the voltmeter will give the initial voltage which we're looking for? Whereas in A the current will keep passing anyway because of the position of the diode so the voltage reading won't be that of the diode when it begins to conduct. Is that what you meant? If so then I got it! :D
 
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please help me with detailed explanation on question number 5 and 14 of 9702/01/M/J/03. Help!!
 
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