Physics: Post your doubts here!

[Ali Ahsan Khilji]

What is the answer to this MCQ?What is the reasoning?Which graph is of glass,steel and rubber?

 

[Oliveme]

Did i get the correct answer??

Yes, yes. You did.

 

[Iffat]

how do you find the time interval using the callibrated time base of a cro?

 

[Warrior66]

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.

 

[Yousif Mukkhtar]

Can some one explain this:
http://www.drivehq.com/file/df.aspx?isGallary=true&shareID=6762768&fileID=466048488
q 27

 

[Iffat]

how do you find the time interval using the callibrated time base of a cro?

can sum1 plz ans ASAP

 

[aalmuhannadi]

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?

 

[daredevil]

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

 

[daredevil]

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.

 

[aalmuhannadi]

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?

 

[aalmuhannadi]

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!

 

[mizmoody]

please helpp!! :/

 

[Iffat]

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

thanx

 

[unseen95]

please help me with detailed explanation on question number 5 and 14 of 9702/01/M/J/03. Help!!

 

[unseen95]

please help at question number 30 of 9702/01/M/J/03 with explanation.

 

[beeloooo]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w02_qp_2.pdf


ANyone can help with waves question ? its urgent . i struggle with the phase angle !

 

[daredevil]

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!

what i mean to say is that the required potential value is of the instant the current reaches the diode. if we use a working diode circuit then we woun't be able to spot that one value as with the passage of current through the diode the value will change. however when current is blocked by the diode then for an instant the current does reach the diode and that instant is recorded, regardless of the fact whether the current keeps flowing through or is blocked.
that is what i understood but anyone if u think it is the wrong answer or there is another CORRECT explanation to the point PLZ help and correct both of us

 

[Muktak Aryal]

Plz Help Me
Question is in the file that i hv uploaded

 

[Trisha Graal Emile]

To make a potentiometer, a driver cell of 4.0 V is connected across a 1.00 m length of resistance wire.
a. a) What is the potential difference across 1 cm length of wire? What length of wire has p.d. of 1.0 V across it?
b. b) A cell of unknown e.m.f E is connected to the potentiometer and the balance point is found at a distance of 37.0 cm from the end of the wire to which the galvanometer is connected. Estimate the value of E. Explain why this can only be an estimate.
c. c) A standard cell of e.m.f 1.230 V gives a balance length of 31.2 cm Use this value to obtain a more accurate value for E.

 

[bogus]

help!!!