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

1. (Original post by Summerdays)
Work done on an object falls as 1/r (or becomes less negative by 1/r if the object has the opposite charge to the point charge) as the distance increases. The force on an object falls as 1/r^2 (or becomes less negative by 1/r^2 if the object has the opposite charge to the point charge) as distance increases. V falls by 1/r and E falls by 1/r^2

The the gradiant of the tangent of a point, in an the electrical potential against r curve, gives the electric field strength at the point. The electric field strength is the gradiant of the potential. The closer together the equipotential lines are the stronger the electric field, and vice versa.
Thanks!
2. (Original post by Birkatron)
Thanks!
No problem I just hope that the explanation helped you. If you have more questions please dont hesitate to ask them
3. oh my god!!!!! is anyone else majorly stressing about this exam? Out of all my exams i was best prepared for chemistry which i need an A in so i tried really hard for that at the expense of physics.. had the exam yesterday was a ridiculous paper and have definitely screwed up! Also need an A in physics and i now feel like there is no hope arrhhhhhhh someone please help me with some physics?! I despise this board!!!!!!!!
4. Can anyone explain the logic behind G495 being before G494?!
5. (Original post by Alex.Stevens)
Can anyone explain the logic behind G495 being before G494?!
Logic?
6. (Original post by Alex.Stevens)
Can anyone explain the logic behind G495 being before G494?!
OCR's genius idea?

they did this with chemistry too. Fantastic.
7. (Original post by 41jms)
oh my god!!!!! is anyone else majorly stressing about this exam? Out of all my exams i was best prepared for chemistry which i need an A in so i tried really hard for that at the expense of physics.. had the exam yesterday was a ridiculous paper and have definitely screwed up! Also need an A in physics and i now feel like there is no hope arrhhhhhhh someone please help me with some physics?! I despise this board!!!!!!!!
This board shouldn't even exist!
8. (Original post by Alex.Stevens)
Can anyone explain the logic behind G495 being before G494?!
OCR and logic rarely appear in the same sentence. Actually the only time they do appear in the same sentence, is when someone's discussing how illogical the course and board are.

Could of had a week free to prepare solely for G495, but now thanks to OCR I have this the day after Maths C4 and a week to prepare for an exam paper shorter than a trip to the toilet
9. (Original post by Swindan)
OCR and logic rarely appear in the same sentence. Actually the only time they do appear in the same sentence, is when someone's discussing how illogical the course and board are.

Could of had a week free to prepare solely for G495, but now thanks to OCR I have this the day after Maths C4 and a week to prepare for an exam paper shorter than a trip to the toilet
exactly how i feel ha. also have c4 on monday. brilliant. this gives us less than 24 hours to revise, yay.
10. how is everyone revising for this? I dont know why id completely neglected it now i dont know where to start!!
11. (Original post by 41jms)
how is everyone revising for this? I dont know why id completely neglected it now i dont know where to start!!
Do some past papers, including the legacy papers. They are very helpful.
12. (Original post by Summerdays)
Do some past papers, including the legacy papers. They are very helpful.
ok, i feel like it has nothing to do with the stuff in the revision guide /stuff weve been taught over 2 years Also is this paper synoptic like chemistry etc is its the last unit?

Also, i know this is asking a bit much but is there anyway you could explain the electrical side of things for me, motors etc in specific?

And if you (or anyone else) have questions post it up and i'll try answering them (im not completely stupid, did get an A last year just majorly stressed right now! ) as i think this would be a good way of revising!!
13. (Original post by Birkatron)
I need an A for Durham blerghhhhh good luck!!
Oh god! Good luck to you too! I'm almost regretting applying to places that need A's in Physics, because its gonna be difficult to achieve!
14. "suggest how an electric field helps to ionise gas" anyone? i thought this was quite hard, i hate wordy questions!!
15. What is physics B, from what I can make out it's like physics A but with some sort of article stuck in it?
16. (Original post by Rothers)
What is physics B, from what I can make out it's like physics A but with some sort of article stuck in it?
STUPID COURSE! (incase you are thinking of taking up a level physics - do not go for this course if you have a choice, you'll regret it like most us! )
17. (Original post by 41jms)
"suggest how an electric field helps to ionise gas" anyone? i thought this was quite hard, i hate wordy questions!!
An electric field produces a force (because virtual photons are the force carriers.) This electric field produces a force in the opposite direction to the field. If the electric force is stronger than the electrostatic force, that is bounding a particular electron to the nucleus, the electron will be emitted. A loss of an electron is ionisation.

That's how I would write it, at least.
18. (Original post by 41jms)
oh my god!!!!! is anyone else majorly stressing about this exam? Out of all my exams i was best prepared for chemistry which i need an A in so i tried really hard for that at the expense of physics.. had the exam yesterday was a ridiculous paper and have definitely screwed up! Also need an A in physics and i now feel like there is no hope arrhhhhhhh someone please help me with some physics?! I despise this board!!!!!!!!
I did the same exam as you I think - I didn't want to know what everyone else though of it 'cause I wasn't too pleased either but I gather that the rest of my year found it tough too so hopefully the grade boundaries will be kind!
I'm in the same position as you - I need all A's but all we can do is stay calm, use the specification thing as law and get as much practice as we can! Try not to panic and don't give up! ^_^
19. (Original post by 41jms)
STUPID COURSE! (incase you are thinking of taking up a level physics - do not go for this course if you have a choice, you'll regret it like most us! )
oh right, well I'm already doing A2 OCR Physics A anyway, just came on this thread to see what Physics B was about, because our school only does Physics A.

Personally I find some of the questions an absolute b**** but at the same time like the challenge, it's just under the pressure of the exam you don't always get time to think about the question, you often have to just dive in
20. look at this guys: http://www.johnbright.conwy.sch.uk/d...03JuneMSA2.pdf

as it doesnt have page number type in the find (Ctrl + F) "cosine curve" it'll take you to the bit im on about.. erm the faint line on the graph is flux linkage. it asks you to draw on the graph how the voltage across the coil changes with time.

Can someone please explain how that markscheme is right?

I thought voltage was proportional to negative gradient. therefore the graph would look a bit different, like stationary points would still be the same but the maxima and minima the other way round?

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