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

1. (Original post by JSaunders9)
Can't use the lens equation because there was no image only two objects
Think of it like this: the eye of that person can handle curvature of -0.8D, so when something has a curvature of -4D, you need to add on 3.2D to correct for the eye.
2. (Original post by HennersPD)
Got this too as 1/u is -0.8
Kind of upset though I think I put 3.2 on the actual paper
3. (Original post by Wolfea)
Think of it like this: the eye of that person can handle curvature of -0.8D, so when something has a curvature of -4D, you need to add on 3.2D to correct for the eye.
yeah taht was what I put on my paper and I am really confused as to what I should have done. I put down 3.2 with that reasoning but now i have my doubts i think its 4.8
4. (Original post by CancerousProblem)
yeah taht was what I put on my paper and I am really confused as to what I should have done. I put down 3.2 with that reasoning but now i have my doubts i think its 4.8
Sorry what was the reasoning behind 4.8? I can't think of any.
5. what did people get for the ratio of resistivities, sensitivity and average current/charge calculations with the voltage temperature graph?
6. (Original post by CancerousProblem)
yeah taht was what I put on my paper and I am really confused as to what I should have done. I put down 3.2 with that reasoning but now i have my doubts i think its 4.8
i got -3.2 to begin with but crossed it out and put 4.8, i think either way there will be one mark for using the equation, even if our answer was wrong
7. (Original post by jack0997)
what did people get for the ratio of resistivities, sensitivity and average current/charge calculations with the voltage temperature graph?

For the ratio I think I got 6.6..that's about as much as I can remember
8. (Original post by Mutleybm1996)
100 and 10khz so 9900

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I got that too
9. (Original post by HennersPD)
Did you get D, C, B for the 3 graphs?
I think i put D A B, can't fully recall sorry. My brain still feels like its been raped
10. (Original post by Mutleybm1996)
Could be have used either resistance for the resistivity one?
Most in my class used 3.14
Some used the 200 and something

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I just put the assumed resistance as 2 ohms, i didnt think you needed to use a previous value as the question said to state assumptions
11. (Original post by IIEquinoxII)
I just put the assumed resistance as 2 ohms, i didnt think you needed to use a previous value as the question said to state assumptions
Do you mean you assume the value of the pd at 35mA is the value for 20 degrees C?
12. (Original post by IIEquinoxII)
I just put the assumed resistance as 2 ohms, i didnt think you needed to use a previous value as the question said to state assumptions
Is this to work out the length? I think I used the resistance at the lowest voltage that we had to work out in table
13. What do everyone think they got btw and please no one say above 50
14. (Original post by Picton2727)
Is this to work out the length? I think I used the resistance at the lowest voltage that we had to work out in table
Yeah

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15. i put 4.8D by using the equation 1/u+1/f=1/u

So i just did -0.8+P=4

so P=4.8D
16. What did you get for the length of the tungsten wire?
17. (Original post by Picton2727)
Is this to work out the length? I think I used the resistance at the lowest voltage that we had to work out in table
Yeah, i just picked 2 ohms as it seemed like a sensible enough number
18. (Original post by CancerousProblem)
What did you get for the length of the tungsten wire?
0.018m?
19. (Original post by CancerousProblem)
What did you get for the length of the tungsten wire?
20. (Original post by jack0997)
0.018m?
I got that too!

did you use the 3.14 ohm resistance then?

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