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# OCR Physics B G495 Field and Particle Pictures June 21st 2011 Exam Thread watch

1. (Original post by kttt101)
did anyone put that the difference in speed of the two wavelengths due to the refraction would cause the superposition effect to break down?

i totally guessed that
That's kind of what I put. I said that the phase difference would start to become more constant as the refractive index decreases and thu the phasors become more and more out of phase - but I totally guessed.
2. (Original post by kttt101)
did anyone put that the difference in speed of the two wavelengths due to the refraction would cause the superposition effect to break down?

i totally guessed that
See my post above, that was what I put . . .
3. (Original post by kttt101)
it wasnt as bad as i thought it would be actually

yeah exactly that.. but i ended up dividing the emf by two... took a risk! if it turns out wrong it will only be a mark
Oh, why did you divide by two, is it because it said average? Hmm... that's a good point.

Yeah, it went better than a lot of the past papers I have done, I think.
4. (Original post by Summerdays)
Oh, why did you divide by two, is it because it said average? Hmmmm... that's a good point.

Yeah, it went better than a lot of the past papers I have done, I think.

yeah i guessed that at the start of rotation it would be cutting virtually no flux and at the end it would cut the max amount of flux which we'd already worked out so i just did half of what i got

it was a bit random. i was expecting the last couple of questions on part b to be a magnetism one which is good because thats my weakest area
5. (Original post by Unkempt_One)
See my post above, that was what I put . . .

ok.. take it from your predicted youre pretty smart so ill take your word for it!:P
6. (Original post by arianex)
Mass of U-235 per year:

Multiply Watts/power given by number of seconds in a year, get total energy used per year.

Divide total energy by energy released per fission to get no of nuclei that decay.

Get actual mass of one U-235 nucleus by multiplying 235 by u to get mass in kg

Multiply no of nuclei by the mass...result?
Cheers mate shame that i didn't get that
7. do we got a post about the upcoming unit4 ?? or do we just stick with here ?
8. (Original post by Summerdays)
Oh, why did you divide by two, is it because it said average? Hmm... that's a good point.

Yeah, it went better than a lot of the past papers I have done, I think.
On the one with the ring, i thought it was an average because of the way the ring was moving. It wasn't spinning it was just sort of falling, so i thought the bottom part of the ring which didn't move much only cut a few lines, whilst the top part covered a larger distance cutting more lines. So i thought the normal calculation could be the average.
9. (Original post by 5liam5)
On the one with the ring, i thought it was an average because of the way the ring was moving. It wasn't spinning it was just sort of falling, so i thought the bottom part of the ring which didn't move much only cut a few lines, whilst the top part covered a larger distance cutting more lines. So i thought the normal calculation could be the average.
I think it did spin, but it only did 1/4 of a rotation. If it just feel without spinning then the flux lines through the area of the coil would be constant, I think.
10. I got 5kg for for the mass or uranium :/ must have put it into my calculator wrong or something
11. (Original post by Summerdays)
I think it did spin, but it only did 1/4 of a rotation. If it just feel without spinning then the flux lines through the area of the coil would be constant, I think.
Aah man i didn't quarter it or anything.. Think i get 0.1V or something.
12. (Original post by kttt101)
it wasnt as bad as i thought it would be actually

yeah exactly that.. but i ended up dividing the emf by two... took a risk! if it turns out wrong it will only be a mark
I used the normal equation, i thought it would be average because the normal flux linkage/time graph is a curve, but we calculated the straight line gradient between the points and 0... so i guessed that our equation didn't take into account this curve?
13. (Original post by Geekchic17)
I used the normal equation, i thought it would be average because the normal flux linkage/time graph is a curve, but we calculated the straight line gradient between the points and 0... so i guessed that our equation didn't take into account this curve?
Yeah that's what I did.

Geekchick, what did you put for the 800 minima question?
14. (Original post by Keckers)
I got 4.35 people and rounded it up to 5. I hate those questions haha

I was generally pretty happy with the paper, hopefully it will be the 2nd A for my durham offer
I did this too
15. (Original post by Summerdays)
Yeah that's what I did.

Geekchick, what did you put for the 800 minima question?
Erm .. The one asking for wavelength?
2d = phase difference i think of n/2(lambda) but n is odd, so i think thats the same as your 2n+1 lambda version?
I can't really remember
I seem to remember i got somehting like 525 nm for a wavelength somewhere down the line ..? it was like 525 accurate so i presumed it was right?
16. Just spotted this:
http://www.bbc.co.uk/news/education-13857911

Was this our physics paper or a different one? Sorry if it's already been mentioned on here.
17. did anyone else get like 4.96 kg for the mass of uranium used??
18. (Original post by LALP10)
Just spotted this:
http://www.bbc.co.uk/news/education-13857911

Was this our physics paper or a different one? Sorry if it's already been mentioned on here.
I think it was OCR A (From what people were saying before)
19. (Original post by Geekchic17)
Erm .. The one asking for wavelength?
2d = phase difference i think of n/2(lambda) but n is odd, so i think thats the same as your 2n+1 lambda version?
I can't really remember
I seem to remember i got somehting like 525 nm for a wavelength somewhere down the line ..? it was like 525 accurate so i presumed it was right?
Yeah, I got 525 nm. The difference between the two answers is minimal.
20. (Original post by vit1008)
did anyone else get like 4.96 kg for the mass of uranium used??
Think i got 2000kg

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