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# OCR PHYSICS B G494~ 11th June 2015 AM ~ A2 Physics watch

1. (Original post by Mutleybm1996)
which paper?
June 2014.

Confident.

Advice/tips - remember the three points for all wordy BF questions and, actually, for all the energy/speed/ideal gas wordy questions - there will always be at least 1.
2. Been getting ~80% in past papers 2006-2014, but I know OCR will have something nasty in store for tomorrow so >_>
3. (Original post by DomStaff)
June 2014.

Confident.

Advice/tips - remember the three points for all wordy BF questions and, actually, for all the energy/speed/ideal gas wordy questions - there will always be at least 1.
what are the "three points"?
4. (Original post by DomStaff)
June 2014.

Confident.

Advice/tips - remember the three points for all wordy BF questions and, actually, for all the energy/speed/ideal gas wordy questions - there will always be at least 1.
what's 1/e? what's e?
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5. (Original post by Mutleybm1996)
what's 1/e? what's e?
e is the base of the natural logarithm.
6. (Original post by Mutleybm1996)
what's 1/e? what's e?
1/e is about 0.37. So basically you can say that the time constant is the time taken for the current to fall to 37% of its initial value. e is just a special number that occurs in exponential relationships its about 2.718 to 4 sf.
7. (Original post by lizard54142)
e is the base of the natural logarithm.
oh!
Yes I do maths so I know all about e, i thought it was referring to the charge on an electron and just thought "what?!"

with the graph, why is it everything to the right, i thought it was everything between R and D

and for the proof, can someone quickly explain what happens between the two highlighted lines? I'm quite a confident mathematician but it's bugging me as I keep ending up with ln(-lambdaN0) and you can't take logs of a negative number...
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8. (Original post by Mutleybm1996)

with the graph, why is it everything to the right, i thought it was everything between R and D
It's everything to the right as potential is from infinity to a point so its from D to infinity.
9. (Original post by will_iredale)
It's everything to the right as potential is from infinity to a point so its from D to infinity.
cheers

10. can someone briefly run through the highlighted lines? I didn't think you could take logs of a negative -lambdaN0???
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11. (Original post by Mutleybm1996)
cheers

I'm not entirely sure about the negative but i believe it's because -lamdaN0 is a constant so i just replaced it with C, took logs then put it back in at the end.
12. (Original post by Mutleybm1996)
can someone briefly run through the highlighted lines? I didn't think you could take logs of a negative -lambdaN0???
You could consider it as , which is just an arbitrary constant, which they have called
13. Say you have gamma and the time taken for observers on Earth
How do you calculate the time taken for observers on a spacecraft?

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14. Multiply it by gamma I think.

Good luck for today everyone - I can usually hit an A* on these papers but OCR have a habit of screwing us over so who knows what will happen...
15. What was the equipotential q?

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16. Did anyone else get 2.7x10^8?
Also I think it went okay....few mistakes but not too bad!

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17. (Original post by tpanesar)
What was the equipotential q?

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I got the one that looked like boobs
Was considering going for the vertical line though

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19. (Original post by STATER)
Yes

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20. (Original post by Mutleybm1996)
Yes

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1-2 mark bump on boundaries you think?

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