A2 Physics P4 Questions ONLY

[boxfire1995]

Man you were so helpful,
May God bless you the only mistake you did was w=+ in the end, it is w=0 in ms. any idea, how?

My sir says it shouldnt be zero. Hes confused too. So, i dont know. He says its supposed to be positive

 

[Champ101]

so4_4: Q5(d ii) Why is it 3.0A? and not 1.12A?

Hey that's totally out of our syllabus. The reason is that the graph is not a sine wave, its square wave. And for square wave, rms =I itself (you don't divide it by root2).

Dont solve old papers, im just solving from 2007, i think this is where they introduced section B (maybe a change of syllabus)

here take a look: http://en.wikipedia.org/wiki/Root_mean_square

 

[Champ101]

Hey guys check this website: http://www.saburchill.com/physics/chapters/0064.html

For R.M.S. concept (great explanation)

 

[Namehere]

so4_4: Q5(a), I don´t get the anwer in the ms.

Paper is some posts above.

 

[lisahamed]

oh yeah! got confused lol btw thats a really smart working bro!

M/J/09 no. 9 (b) please? :3

 

[Namehere]

may 2005 q 7 c pls ASAP

yeah someone please ^^

 

[scouserlfc]

so4_4: Q5(a), I don´t get the anwer in the ms.

Paper is some posts above.

Its just the definition of rms with reference to the heating effect you need to learn that for the exam so probably learn from the book or somewhere.
RMS value of an ac current is that direct current value which gives the same average power as the ac current to a resistor .

SO just modify this definition and instead of power write rate of dissipation of heat energy.

 

[scouserlfc]

may 2005 q 7 c pls ASAP

let x be mass of maganese in micro grams.
then,
(1.4-x)/x = 9
x=0.14 micro grams

Now use number of nucleons equation at time t equation.
N=N0* e^(lambda*t)
(0.14*10^-6 /56) *Avogdros Number = (1.4*10^-6 /56)* Avogadros Number *e^(lamda*t)

lambda=(0.693/2.6*60*60)

Now use the above equation to get the answer of 8.6 hours.

 

[hope4thebest]

and on the same question paper, Q5(a), I don´t get the anwer in the ms.

rms value is only applicable for sinusoidal waves

 

[Namehere]

let x be mass of maganese in micro grams.
then,
(1.4-x)/x = 9
x=0.14 micro grams

Now use number of nucleons equation at time t equation.
N=N0* e^(lambda*t)
(0.14*10^-6 /56) *Avogdros Number = (1.4*10^-6 /56)* Avogadros Number *e^(lamda*t)

lambda=(0.693/2.6*60*60)

Now use the above equation to get the answer of 8.6 hours.

the question is worth 2 marks, isn´t there another easier way? The markscheme says something different.

 

[scouserlfc]

the question is worth 2 marks, isn´t there another easier way? The markscheme says something different.

Its actually the same thing they just skipped all those steps and used 1/10 th of original mass which is 0.14 micro grams as i said u can do that as well but u still need to go through this process as u need to use the ratio . Its an old paper so no wonder it just gives u 2 marks for this much trouble.

 

[Namehere]

Someone help me on Q9(all)

Thanks!

 

[hope4thebest]

Why emf induced in the secondary coil not in phase with emf in the primary coil?

 

[Ahsen chaudhry]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w13_qp_43.pdf

Question number 6 b i How do we know the direction of the magnetoc field ? and 6 c ??

 

[goodluckayesha]

Plz someone explain these quickly thnx in advance........

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s04_qp_4.pdf for 5ci how is the ratio 2 i get the formula but im not getting the answer and for 5dii why is the rms 3A?

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w02_qp_4.pdf 2b which is actually a really easy question but im confused it would be really helpful if someone provides a drawn n labelled diagram

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w04_qp_4.pdf can anyone solve 6c with steps i cant get thru

 

[boxfire1995]

Please can someone explain to me emission and absorption spectra?

 

[axetreme.O]

How is n/N=Na (avogadro constant) ?

 

[boxfire1995]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s03_qp_4.pdf
Question 2. Can someone explain it to me please!!!!

Internal energy is the sum of random kinetic and potential energies at the molecular level, okay? Now, kinetic energy increases when theres an increase in temp and potential energy increases when the distance between molecules increases.
So, lets consider the first option, water freezing at constant temp. Temp constant means no change in kinetic energy, right? And freezing means molecules coming closer. So, there is a decrease in potential energy. Thus internal energy decreases.
Second option, a stone falling under gravity in vacuum, this has no effect on the molecules of an object, thus nope.
Third option, water evaporating at constant temperature. Temp is constant, no change in ke, but since in evaporation, molecules get further apart, a rose in potential energy it is indicating and thus a positive change in internal energy.
Fourth, constant temp, no change in ke. Stretching, molecules get further apart, inc in pe and thus internal energy.

 

[boxfire1995]

the second part???????

Wait, for five minutes and ill answer it.

 

[boxfire1995]

Wait, for five minutes and ill answer it.

Ive done exactly the thing they have asked in the marking scheme, but im not getting the right answer. My answer is 1200k.