A2 Physics | Post your doubts here

[Jonathan127]

Has anyone done October/ November 2005?

Q6 c) (ii) I don't understand how to sketch that graph?
http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_w05_qp_4.pdf

 

[Mobeen]

No, the thumb shows the direction of the movement, the first finger/ index finger shows the direction of the field, and the the second finger shows the direction of the induced current/ EMF.

i was talking about the movement of a proton in a magnetic field cause she asked where the protons come in this rule .. i wasnt talking about emf

 

[Jonathan127]

thank god! I thought I was making physics up! ... do we need to know anthing about the stopping potential?

No you don't need to know about the stopping voltage but I'm pretty sure you need to know about the threshold frequency. Just learn it anyway though, cause I remember the mark scheme mentioning it once.

 

[Mobeen]

thank god! I thought I was making physics up! ... do we need to know anthing about the stopping potential?

i dont know myself what stopping potential is

 

[angelicsuccubus]

No, the thumb shows the direction of the movement, the first finger/ index finger shows the direction of the field, and the the second finger shows the direction of the induced current/ EMF.

yeh and induced current is taken in the conventional direction.. which means its the flow of positive particles, protons not electrons... but its okay if you believe that its electrons flowing from the positive terminal to the negative terminal, cause that totally makes sense right? =p

 

[Mobeen]

Has anyone done October/ November 2005?

Q6 c) (ii) I don't understand how to sketch that graph?
http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_w05_qp_4.pdf

for T1 to T2 there would be a horizontal line above the axis . and for T2 to T3 there would be a horizontal line below the axis . everywhere else would be at zero .

 

[angelicsuccubus]

i dont know myself what stopping potential is

stopping potential, Vs, is the potential (voltage in a photocell) at which the photoelectrons don't have enough energy to go from the positive electrode (cathode) to the negative electrode (anode). This is like the maximum potential at which they have maximum kinetic energy. .. they can't get past it.

0.5mv^2 (max)= eVs where e=-1.6x10^-19 but you don't take the negative in account during calculation.

This makes the eqution : hf= hf. + k.e the same as hf= hf. + eVs
hf.=work function

 

[Jonathan127]

for T1 to T2 there would be a horizontal line above the axis . and for T2 to T3 there would be a horizontal line below the axis . everywhere else would be at zero .

But, like how do you know?

 

[Mobeen]

stopping potential, Vs, is the potential (voltage in a photocell) at which the photoelectrons don't have enough energy to go from the positive electrode (cathode) to the negative electrode (anode). This is like the maximum potential at which they have maximum kinetic energy. .. they can't get past it.

0.5mv^2 (max)= eVs where e=-1.6x10^-19 but you don't take the negative in account during calculation.

This makes the eqution : hf= hf. + k.e the same as hf= hf. + eVs
hf.=work function

oh ok thanks ! but havnt seen any question regarding this , or is there?

 

[Mobeen]

But, like how do you know?

E is the rate of change of magnetic flux density. from T1 to T2 variation in B is constant i.e the gradient is constant . so a horizontal line is sketched . same goes for t2 to t3 but in opposite direction ..
you simply have to sketch the gradient per unit time for the above graph .. get it ?

 

[angelicsuccubus]

oh ok thanks ! but havnt seen any question regarding this , or is there?

I wouldn't know.. I'm just reading a physics book.. so if you see on, let me know =]

 

[Jonathan127]

E is the rate of change of magnetic flux density. from T1 to T2 variation in B is constant i.e the gradient is constant . so a horizontal line is sketched . same goes for t2 to t3 but in opposite direction ..
you simply have to sketch the gradient per unit time for the above graph .. get it ?

Oh right! Now I get it. Never thought about it like that. Thanks

 

[Mobeen]

I wouldn't know.. I'm just reading a physics book.. so if you see on, let me know =]

sure thing .

 

[Mobeen]

Oh right! Now I get it. Never thought about it like that. Thanks

np . its quite simple you just have to see it right !

 

[angelicsuccubus]

What chapters are most of the questions in the past papers from?

 

[angelicsuccubus]

people don't leave me alone.... physics tends to become scary!

 

[Jonathan127]

people don't leave me alone.... physics tends to become scary!

Um, I really can't say. I've answered a lot of Gravity questions, and motion in a circle questions as well. You can't predict what will come.
Have you read the application stuff? Sometimes there are 6 - 8 mark questions in that!

 

[angelicsuccubus]

Um, I really can't say. I've answered a lot of Gravity questions, and motion in a circle questions as well. You can't predict what will come.
Have you read the application stuff? Sometimes there are 6 - 8 mark questions in that!

what application stuff?.. so far I've read photoelectric effect and wave particle duality, emission and absorption spectra, temperature change and latent heat

 

[optimistic]

Hey folks,
please explain me this question! Q6 part b1 and and part c of MAY/JUNE2009, Q9 of MAY/JUNE 2009, and Q10 c2( my answer is coming as 10V but in M.S it is 9.0V)
http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s09_qp_4.pdf

 

[angelicsuccubus]

people wth is all this derivation of weird equations in the ideal gases chapter? do I neeed to know them?