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# OCR PHYSICS B G491~ 19th May 2015 AM ~ AS Physics watch

1. (Original post by lauren_2)
When using log2 (Vtotal/Vnoise) and the answer is a decimal e.g. 2.8 do you use the integer number of bits below or above? E.g. 2 or 3? I always believed it was below but last years paper it only allowed above? Sorry if this is obvious, I am very confused ahaha
This is question dependant, most of the time if you're working it out, round up.

However if you're asked why there's no point in using 4 bits given that log2(vtotal/vnoise) =3.213, you'd have to say something a long the lines of:

No point in using 4 bits as any value greater then 3.2 will introduce noise, so 3 bits must be used, as an integer value is required for the number of bits.
2. (Original post by SheLikeTheMango)
Hey, ive learnt the content over the year but what is an effective method for quickly going over everything on one day? Should i make flashcards and write notes? Im also doing past papers aswell.
I'm just gonna read through em and maybe rewrite some materials notes

Mainly past papers though

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3. (Original post by Zallin98)
Not Brilliant! Looking through the content for the first time now! :L
Hah! Did you just forget or something?

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4. (Original post by IIEquinoxII)
In the examiners report for last years paper they admit that they messed up big time, and noted that the timing was way off. Im 99% sure this paper will not be anywhere near as hard
I'll quote you on that (literally!). Hoping for more calculations as I HATE MATERIALS with a passion!! let's hope its much easier, no QR codes rubbish :L anyone doing aqua core 2 maths on Wednesday?
5. Anyone else agree with this...?

(Original post by HennersPD)I completely agree! After last years debacle of a paper I'm really worried for this year! Just hope they'll be kind and give us something nice!

QUOTE: In the examiners report for last years paper they admit that they messed up big time, and noted that the timing was way off. Im 99% sure this paper will not be anywhere near as hard

Who thinks this years paper will be easier as a response to last year being so bad? I'm resitting so would like to know people's thoughts
6. (Original post by HennersPD)
I'll quote you on that (literally!). Hoping for more calculations as I HATE MATERIALS with a passion!! let's hope its much easier, no QR codes rubbish :L anyone doing aqua core 2 maths on Wednesday?
I agree with you that materials is a pain in the arse, but i didnt think the qr code question was difficult to be honest.
7. (Original post by IIEquinoxII)
I agree with you that materials is a pain in the arse, but i didnt think the qr code question was difficult to be honest.
ah ok, so do you think this years will be easier than last year? which topic are you least confident on?
8. (Original post by HennersPD)
ah ok, so do you think this years will be easier than last year? which topic are you least confident on?
It will almost certainly be easier than last year, but whatever happens, the grade boundaries will shift to account for it so it shouldn't really matter.
My weakness is in materials, i do chemistry so whenever i get questions about material structures i instinctively start writing the answer i would write in a chemistry exam. But then i drop tons of marks for forgetting to include key terms etc.
9. (Original post by IIEquinoxII)
It will almost certainly be easier than last year, but whatever happens, the grade boundaries will shift to account for it so it shouldn't really matter.
My weakness is in materials, i do chemistry so whenever i get questions about material structures i instinctively start writing the answer i would write in a chemistry exam. But then i drop tons of marks for forgetting to include key terms etc.
haha funny i am the exact same as I'm resitting this module knowing a2 chem is really annoying since i try to overcomplicate my answers for the materials questions in g491 :/
10. [QUOTE=Bruhh;55917025]
thanks they were both useful, do you have pdfs for the other topics?
11. [QUOTE=Bruhh;55917025]These 2 pdfs are pretty helpful for pretty much all the materials stuff.

thanks these were very useful
do you have pdfs for the other topics?
12. has anyone got like a list of definitions for tomorrow? i keep tripping up when it comes to terms like polycrystalline etc...
13. (Original post by lyricalvibe)
Hah! Did you just forget or something?

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Erm... im just good at procrastinating! :L
14. (Original post by AndrewC19)
This is question dependant, most of the time if you're working it out, round up.

However if you're asked why there's no point in using 4 bits given that log2(vtotal/vnoise) =3.213, you'd have to say something a long the lines of:

No point in using 4 bits as any value greater then 3.2 will introduce noise, so 3 bits must be used, as an integer value is required for the number of bits.
Sorry to keep going on but why was it 9 bits and not 8 in question 3 June 2014? Wouldnt this introduce noise?
15. (Original post by lauren_2)
Sorry to keep going on but why was it 9 bits and not 8 in question 3 June 2014? Wouldnt this introduce noise?
Think of it this way, it asks you how many bits you should use for each sample. So you calculate log2(400)=8.6

Suppose you use 8 bits, you're losing data as you're ignoring that extra 0.6.

Using 9 bits ensures that you're accounting for all data.

Basically whenever you have to calculate bits per sample, round up as you want to include all data.
16. [QUOTE=terrytomlinson;55928771]
(Original post by Bruhh)
These 2 pdfs are pretty helpful for pretty much all the materials stuff.

thanks these were very useful
do you have pdfs for the other topics?

Hopefully the download works! This contains both AS and A2 revision material for OCR B. Just unzip and extract the main folder than execute the 'autorun.bat' file and it'll display it like this:
17. (Original post by Rolochlo)
Can anyone give any decent explanation on bandwidth please?? Everything about this exam is driving me insane! Confidence is non-existant for this now too XD
bandwidth is a range of frequencies within a signal .if you want to calculate the bandwidth you just subtract the lowest frequency from the highest frequency.Also remember that bandwidth limits the number of signals transmitted because you need to leave a gap between each bandwidth so that they dont overlap eg for radio channels, tv programmes etc
18. (Original post by HennersPD)
haha funny i am the exact same as I'm resitting this module knowing a2 chem is really annoying since i try to overcomplicate my answers for the materials questions in g491 :/
I feel like OCR B dumb down physics a bit too much, they say that the electrons in metallic bonding act as a 'glue'...
19. (Original post by SheLikeTheMango)
I feel like OCR B dumb down physics a bit too much, they say that the electrons in metallic bonding act as a 'glue'...
oh yeah haha so childish :L
20. http://www.cram.com/flashcards/g491-...hysics-5861979

I HAVE JUST MADE A FLASHCARD SET ON CRAM REGARDING TOMORROW!

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