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AQA Physics PHYA4 - Thursday 11th June 2015 [Exam Discussion Thread]

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Original post by Protoxylic
I think I'm on for full marks with MC, with the only exception being the last Q on MC I said it was to increase mechanical stability. MC was fairly standard, 2-3 repeated Qs. Long answer was pretty good (bar the emf 2 marker oops). 1a was weird since you couldn't mention specific phase differences for forced vibrations as it is a range from 0 to pi/2 and pi/2 to pi (not inclusive of pi/2 as that is resonance). So I'm interested to see the mark distribution for that. Unit 5 is alright, I just hate turning points so we will see how that goes. Thanks, you too :tongue:


Think you were right in saying that the steel core increases mechanical stability, this is what I'm reading when I google 'why do power lines have steel cores?'. I don't think the other answers made sense.
Reply 4621
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J1995x
Original post by djw0bbl3
Please, someone reassure me that I'm not the only one who thinks that was awful? I'm really angry and upset :frown: It was just full of so many ****ty questions. I need some reassurance.



Yeah don't worry, you're definitely not the only one there. Going all British and grabbing a hot drink helps. Just got to remember it's not the end of the world. What's the worst case scenario? Having to retake, or no uni place. There's other good things in your life :smile:
Any idea on what the grade boundaries will be?
Original post by Fvthoms
Can you post the values provided in the question that you remember? Wanted to check workings, but calculator cleared itself.

I can't remember them, sorry.

Original post by Protoxylic
I think I'm on for full marks with MC, with the only exception being the last Q on MC I said it was to increase mechanical stability. MC was fairly standard, 2-3 repeated Qs. Long answer was pretty good (bar the emf 2 marker oops). 1a was weird since you couldn't mention specific phase differences for forced vibrations as it is a range from 0 to pi/2 and pi/2 to pi (not inclusive of pi/2 as that is resonance). So I'm interested to see the mark distribution for that. Unit 5 is alright, I just hate turning points so we will see how that goes. Thanks, you too :tongue:

Yeah the MC was okay. What was the answer for the last question?
I'm doing the astrophysics option. It sucks. It's not hard, but there's a lot to remember. Fortunately the grade boundaries are low as ****.
anyone thinking of putting together an unofficial markscheme?:smile:
Original post by StarvingAutist
I can't remember them, sorry.


Yeah the MC was okay. What was the answer for the last question?
I'm doing the astrophysics option. It sucks. It's not hard, but there's a lot to remember. Fortunately the grade boundaries are low as ****.


It was to increase mechanical stability apparently. I was just unsure as it was a bit GCSE-esque. The other 3 answers definitely didn't seem correct as adding steel in parallel would increase resistance (very slightly) and it wouldn't force all current to go through the outer wires as that already occurs in absence of the steel core. I wanted to do applied, but got stuck with turning points lmao. The wording is so odd and it has the lowest grade boundaries of the 4 (5?) option topics. One year you needed 9/35 on that paper to get an E on that section lmao
For P and Q what would you think I would get to :

(i) Current flowing through (which has magnetic flux) this with less resistance initally hence the reading on ammeter would be high (mentioned about flux cutting too)

(ii) There is resistance so accoring to R= 1/CUrrent, if resitance is high current would e low hence the reading on ammeter would be less than in (i)

Would this gain few marks?
Hahaha
Original post by danphil
Thanks
Original post by oonic0rn
anyone thinking of putting together an unofficial markscheme?:smile:


i hope not, i dont want to cry myself to sleep tonight
Original post by RemainSilent
For P and Q what would you think I would get to :

(i) Current flowing through (which has magnetic flux) this with less resistance initally hence the reading on ammeter would be high (mentioned about flux cutting too)

(ii) There is resistance so accoring to R= 1/CUrrent, if resitance is high current would e low hence the reading on ammeter would be less than in (i)

Would this gain few marks?


for II) i did the same, its pretty basic thinking so you can't go wrong there.

for I) I literally had no idea haha just did some other crap hoping it pulled a mark out.
Just remembered about the one where it asks for the unit I put Wb, now I'm thinking I should have put Wb Turns..
Original post by ShutUpLegs
Just remembered about the one where it asks for the unit I put Wb, now I'm thinking I should have put Wb Turns..


I did the same thing, reallyyyyy regretting it but im thinking they may not mind seeing as N isn't really requiring a unit. so maybe we're okay ^^
Original post by Protoxylic
It was to increase mechanical stability apparently. I was just unsure as it was a bit GCSE-esque. The other 3 answers definitely didn't seem correct as adding steel in parallel would increase resistance (very slightly) and it wouldn't force all current to go through the outer wires as that already occurs in absence of the steel core. I wanted to do applied, but got stuck with turning points lmao. The wording is so odd and it has the lowest grade boundaries of the 4 (5?) option topics. One year you needed 9/35 on that paper to get an E on that section lmao

Oh, good. That's one less mark to have lost :lol:

9, wtf? That's mad!
grade boundary ideas?
Original post by Razzamataz179
i hope not, i dont want to cry myself to sleep tonight


ahhaah i need closure!!
Hello guys, I know the unit for Flux Linkage is Wb Turns, but I missed of the turns and wondering if they have any lenience to this, for some reason I think it's come up before.
Reply 4636
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96wst
1
Does anyone agree with this:
Over the past 5 years, the unit 4 paper difficulty has varied only slightly. June 2014 was hard (I thought) yet the grade boundaries were high. The grade boundaries, for 120 ums at least, have only increased.
69,67,63,63,62,62,61
These are the raw marks for 120 ums going from most recent.
The june 2015 paper wasn't hard but it wasn't easy- so the grade boundaries should be average. Does anyone have any estimations for A*? last year was 61, so i think it may be higher :frown:
Original post by oonic0rn
ahhaah i need closure!!


aha you say that now :P
any chance you remember how many marks the electric field, work done and emf questions were worth?
Original post by RemainSilent
For P and Q what would you think I would get to :

(i) Current flowing through (which has magnetic flux) this with less resistance initally hence the reading on ammeter would be high (mentioned about flux cutting too)

(ii) There is resistance so accoring to R= 1/CUrrent, if resitance is high current would e low hence the reading on ammeter would be less than in (i)

Would this gain few marks?


In (i) there's a sudden change in flux through Q so a current flows in Q. After that, the flux through Q is no longer changing to there is no current in Q. Result is that the ammeter deflects and then returns back to reading zero.

(ii) There's a sudden decrease in current through P, so a sudden decrease in flux through Q so a current is induced in Q in the opposite direction to when the switch was closed (before, there was an increase in flux). Then afterwards the flux through Q is constant so no current in Q. Result is that the ammeter deflects in the opposite direction to before and then returns to zero.

There was nothing to suggest that the current in Q in (ii) should be less than that in part (i).
look, hard paper or not, its all relative. Wev all found those wordy questions difficult and it was easy to lose marks on the rest of Section B today. that being said it wasn't a particularly challenging section A althought 4 or 5 where kinda discriminating. what im saying is they could have given us the easiest paper ever, but if WE AS A NATION did awful then the boundaries would be low. Today, if people are saying its easy then the boundaries may not fully reflect this as its all about how we actually did

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