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# AQA Physics PHYA4 - 20th June 2016 [Exam Discussion Thread] watch

1. (Original post by tanyapotter)
i think it's B too, but is this the right answer?
Ooops
2. (Original post by Jay1421)
5ms^-1

Hope it helps!
thanks, what was the question/solution? I cant remember and now it makes me paranoid haha
3. (Original post by notanooblol)
It asked for time constant, RC
Was -45/ln(0.8) involved at all in that question?
4. for the first capacitor question on the written paper, were we supposed to find the gradient or area?
5. (Original post by SRaccount)
Was -45/ln(0.8) involved at all in that question?
nope it was -45/ln(0.2)
6. (Original post by particlestudent)
What would 54 to 58 marks be?
A decent mid A grade. Good job. I think I got 51-54. I really messed up on the graph, proof and the electromagnetic brake question :/
7. (Original post by KellyLouise0)
for the first capacitor question on the written paper, were we supposed to find the gradient or area?
8. (Original post by notanooblol)
How many people managed to do the derivation? It seemed like one of the hardest parts of the paper
I did it but I don't think anybody else got it at my school
(Original post by SRaccount)
Was -45/ln(0.8) involved at all in that question?
It was ln0.2
9. (Original post by duncant)
thanks, what was the question/solution? I cant remember and now it makes me paranoid haha
Okay so, the graph that you drew was basically a Force / Time graph and it asked you to calculate the speed of a 2kg mass after the 1 second time frame. So you calculate impulse using area under the graph:

[ (0.5 * 5) + (0.5 * 15) ] = 10 = delta (mv)

so Impulse, 10, divided by mass, 2, = velocity => 5ms^1
10. (Original post by C0balt)
Yes I got these, the transformer was repeat from another year wasn't it
I can't remember off top of my head but if you ask I might remember. I got C^2kg^-1 as the EG one is all I remember lol

You might get a mark but I couldn't tell, because this was a new question
I got C^2kg-2 for the ε0G unit
11. That's good, the six marker was very simple so they had to make it harder in some way, so glad I managed it
12. (Original post by C0balt)
I did it but I don't think anybody else got it at my school

It was ln0.2
I would've done that derivation if it werent for the fact my equation stated that the unstable nucleus had a momentum before decay.... anything x 0 is 0. I feel like an idiot.
13. (Original post by SRaccount)
Was -45/ln(0.8) involved at all in that question?
the time constant question was RC= -45/ln(0.2) not 0.8 because the pd decrased BY 80% not to 80%. the answer was about 28 I think. If you used 0.8 I think you bgot about 200 possibly?
14. For the MC question with 8 graphs (picking the two for charging a capacitor I believe? with C/V on one y-axis and I (Current) on the other? I put the one with the C/V graph going up but the rate decreasing exponentially and the amplitude graph going down exponentiall (Becuase I think current always decreases with capacitors) Is this right?
15. (Original post by SirRaza97)
A decent mid A grade. Good job. I think I got 51-54. I really messed up on the graph, proof and the electromagnetic brake question :/
I messed up on proof and the em brake question too. I had a hard time explaining em induction in words.

Did the wheel actually induce an emf which in turn opposed the change of flux linkage in the current? It really confused me...
16. (Original post by notanooblol)

That's good, the six marker was very simple so they had to make it harder in some way, so glad I managed it
Yeah was surprised to see that six marker, ISA was very similar
17. (Original post by spmenz123)
I got C^2kg-2 for the ε0G unit
nice I guessed that one and got the same :P
18. (Original post by willfmair)
For the MC question with 8 graphs (picking the two for charging a capacitor I believe? with C/V on one y-axis and I (Current) on the other? I put the one with the C/V graph going up but the rate decreasing exponentially and the amplitude graph going down exponentiall (Becuase I think current always decreases with capacitors) Is this right?
19. C
B
A
D
C
C
D
B
B
C
A
A
C
A
C
A
D
A
C
A
A
D
B
A
D

20. (Original post by willfmair)
For the MC question with 8 graphs (picking the two for charging a capacitor I believe? with C/V on one y-axis and I (Current) on the other? I put the one with the C/V graph going up but the rate decreasing exponentially and the amplitude graph going down exponentiall (Becuase I think current always decreases with capacitors) Is this right?
Yes. Think this was A

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