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# AQA Physics Unit 1 PHYA1 20th May 2013 watch

1. (Original post by Tuya)
It only makes a difference at the 4th sig fig, so it doesn't matter, but I did include it anyway...

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Oh, ok great. Because I thought I saw someone say that it's wrong if you do

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2. My answers to the numerical questions, in order of how they were in the paper, not guaranteed to be right but just.. yeah

1. 20 protons
2. 28 neutrons
3. 18 electrons
4. 3.2 x 10^-19
5. 4.2 x 10^6
6. 1.8
7. 4.4
8. 128
9. 64
10. 45 v
11. 100 HZ
12. 6.3
13. 5.7
14. 2.85
15. 1.35
16. 4.2
17. 2.9
18. 26.46 W
19. 16.245 W
20. 7.695 W
21. 50.4 W
22. 6.7 x 10^-5
23. 0.33
24. 3 x 10^4 ohms

also 16V as the division for Y, and 2ms for the time base per division
3. (Original post by GeneralOJB)
For 0.75 to pass through the 5k resistor, the current must be 0.75/5000 = 1.5x10-4 A. This means the overall resistance must be 6/1.5x10^-4 = 40000 ohms. You already have 5000 ohms on the resistor R and 5000 ohms on the LDR which you were given, so the variable resistor must be 40000-5000-5000 = 30000 ohms.
How many marks would I get for 30K ohms

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4. did we have to draw a line for rms voltage or just calculate it?
5. (Original post by hannahclaire)
you know on the specific charge one on question one, I completely forgot to add the mass of the electrons, kicking myself for making such a stupid mistake!

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It only makes a difference to the 4th sig fig apparently so youre alright

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6. (Original post by Jimmy20002012)
How many marks would I get for 30K ohms

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That's fine, assuming the examiner knows what K means.
7. Unfortunately that was an easy exam that i got a lot of questions wrong in, the grade boundaries will probs be low cos there were no reaallly hard questions. Bad times
8. The answer to that last question was 4
9. (Original post by BenChard)
did we have to draw a line for rms voltage or just calculate it?
Both. The question that asked you to draw on figure 2 the equivalent DC with the same rate of energy dissipation yadda yadda, was just asking you to draw the RMS line.
10. Where did the DC equivalent line go? Does it go above the peak or where the rms value would go?

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11. (Original post by KES4lyf)
My answers to the numerical questions, in order of how they were in the paper, not guaranteed to be right but

also 16V as the division for Y, and 2ms for the time base per division
wasn't it already at 2ms on base and it only fitted one so you need 4ms?
12. (Original post by usycool1)
2, I think, not many.

Can't remember, except I know I got 30000 ohms on the last one or something
I got 83000 :/

Oh my god

but it seems to work:

6 x 11000/83000+ 5000 = 0.75 V

& that 11000 you can confirm like this:

0.75/ 11000 = 6.8 x 10^-5 A

I = V/R = 6 / 11000+83000 + 5000 = 6.0 x 10^-5

Okay the currents are different damn it Just realized I can expect zero marks I guess

For the first question did you do multiply charge by 2 or 18 ? I did 18, if so how many marks can I expect to lose out of the 3 ?
13. (Original post by Notorious544d)
For the oscilloscope question, I did 20v per division not 16v. Will they both be accepted, so like in the mark scheme, will it say 'accept any sensible value?' I'm guessing the main thing about the question was that you had to write that the time base had to be set at 2ms per division so that the two cycles can be seen. Hmm...
I did that as well, 20Vdiv-1 but I stupidly put 0.5msDiv-1 instead of 2msDiv-1
14. (Original post by FrankB3)
Where did the DC equivalent line go? Does it go above the peak or where the rms value would go?

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The RMS value - 45v.
15. (Original post by GeneralOJB)
Both. The question that asked you to draw on figure 2 the equivalent DC with the same rate of energy dissipation yadda yadda, was just asking you to draw the RMS line.
damn didn't see that bit
16. (Original post by FrankB3)
Where did the DC equivalent line go? Does it go above the peak or where the rms value would go?

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Rms I think

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17. How many marks do you think you would have to lose to not get an A?
18. Didn't think the paper was ridiculously hard! Think there will be quite high grade boundaries!

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19. (Original post by KES4lyf)
My answers to the numerical questions, in order of how they were in the paper, not guaranteed to be right but just.. yeah

1. 20 protons
2. 28 neutrons
3. 18 electrons
4. 3.2 x 10^-19
5. 4.2 x 10^6
6. 1.8
7. 4.4
8. 128
9. 64
10. 45 v
11. 100 HZ
12. 6.3
13. 5.7
14. 2.85
15. 1.35
16. 4.2
17. 2.9
18. 26.46 W
19. 16.245 W
20. 7.695 W
21. 50.4 W
22. 6.7 x 10^-5
23. 0.33
24. 3 x 10^4 ohms

also 16V as the division for Y, and 2ms for the time base per division
I pretty much got the same answers as you

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20. (Original post by Notorious544d)
For the oscilloscope question, I did 20v per division not 16v. Will they both be accepted, so like in the mark scheme, will it say 'accept any sensible value?' I'm guessing the main thing about the question was that you had to write that the time base had to be set at 2ms per division so that the two cycles can be seen. Hmm...
So did I

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