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

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Original post by SirRaza97
Can anyone explain eddy currents and how they are formed?


eddy currents are formed by a changing magnetic flux in the conductor of a transformer etc. The changing flux induces and emf in the core and therefore a current in the core.
Original post by SirRaza97
Can anyone explain eddy currents and how they are formed?


In a continuous core (basically made from one piece of metal) we get eddy currents. This is because the magnetic flux in the core is continuously changing. The change in magnetic flux induces an emf within the core - the circuit will be complete which allows current (eddy currents to flow).

These can be eliminated by separating the core into layers and using insulator between the layers. The insulator prevents a power loss due to heating effect because the current can't flow through them
Original post by mgill17
ISAs must screw over so many students, like there's kids at my college after A*s in physics who got what our teacher reckons will probably be a D or C in their best ISAs. We literally all got Us and Es in the first ISA at my college and we'd done about 6 practice ones since September.

The worst part is it's at a point now where you have to cheat to even be equal with the other centres that cheat. Like the ones of us who actually sat this exam fairly and proper are the ones disadvantaged and AQA overlooked that for so many years. Shame they didn't scrap them earlier or implement some way of controlling the cheating.


Essentially the same scenario here. Though since it's so widespread, maybe Universities are used to dealing with it and will be more likely to admit people who miss their grades because of ISAs over people who missed the grade in the 1, 2, 4 and 5 exams
(edited 7 years ago)
Original post by rory58824
That's around 45 UMS, I think. Just below an A grade (basing off last years boundries)


Original post by TajwarC
Between 42 and 44 I'd say. That's if the boundaries don't go down


Original post by mgill17
That is usually just a B or one mark into the B boundary so I'd go 42/44 UMS.


In June 2014 it was 50UMS... do you think it'll be that low this year? :s-smilie:
Same as June 10 as well
(edited 7 years ago)
Original post by doshea1311
eddy currents are formed by a changing magnetic flux in the conductor of a transformer etc. The changing flux induces and emf in the core and therefore a current in the core.


Which causes energy loses as via unnecessary heating , they can be reduced by laminating the iron core in layers.
Original post by particlestudent
In June 2014 it was 50UMS... do you think it'll be that low this year? :s-smilie:
Same as June 10 as well


I think it's hard to tell because, like others have said, some schools unfortunately cheat.
Original post by rory58824
I think it's hard to tell because, like others have said, some schools unfortunately cheat.


True. Means I need to get around 105UMS in each Unit 4 and 5 to get an A :frown:. Hopefully Unit 4 won't be too bad then...
Any predictions on the 6 marker?
Original post by MintyMilk
Essentially the same scenario here. Though since it's so widespread, maybe Universities are used to dealing with it and will be more likely to admit people who miss their grades because of ISAs over people who missed the grade in the 1, 2, 4 and 5 exams


I think universities are aware of how ridiculous the ISA system is - I got an E in my AS chemistry ISA (my school outright refused to believe that there was even more than one available to do so we didn't even get to retake) - this lead to my AS chemistry grade ending up as a C - I applied for Chemistry. I actually spoke to my interviewer about it when we discussed why my AS grade was relatively low - I ended up getting the offer.

If they see you did well in the exams but poorly in the ISA I don't think it will count against you as much as doing badly in the exams, unless it's Oxbridge
(edited 7 years ago)
Original post by lucabrasi98
I live in north london and 5 out of the 6 closest schools to us cheated in at least one ISA (I have friends in each school). Then there's just our sixth form being legitamate. As a result we all get like 30-45. Meanwhile there's classes where the lowest mark is 45. It's such a pisstake. One of my friends teachers literally talked them through the answers and of course he got 49. He only lost a mark because he drew a point wrong on his graph.

If that many schools near ours our cheating then I can't imagine how bad it must be in the rest of the country.


I'm in West Yorkshire but the closest colleges to me all do the EMPA or they're not on AQA so it's hard to compare up here, but I'm not surprised to hear that about other schools at all. They're the one's laughing when they get into the best unis with their A*s without doing half as much grovelling in the papers where the honest ones need to average near to full UMS in both the exam papers due to a B in their ISA.

The exams office at ours keep them controlled until the morning of the ISAs and there's a very strict in and out policy they have concerning how our teachers can handle the papers and our teachers try to guess what might happen based on the practical. The first one our teacher totally got wrong, he thought it might be capacitance related and it really wasn't. The second one he was a bit closer with but in the end it only really helped us get 4 marks for a derivation and even still not everyone could do it because obviously some people didn't look at it because he'd predicted the previous one wrong.

I don't know how they don't see how colleges with such exclusively high marks and instantly investigate into it. It really isn't fair.
Original post by lucabrasi98
Meanwhile there's classes where the lowest mark is 45. It's such a pisstake.


How do AQA not see this and investigate? Utter ********, or at least give a way for students to report cheating; it's not fair how it can affect someone's future. It devalues any work you do for it
Original post by MintyMilk
Essentially the same scenario here. Though since it's so widespread, maybe Universities are used to dealing with it and will be more likely to admit people who miss their grades because of ISAs over people who missed the grade in the 1, 2, 4 and 5 exams


Maybe they'd assess that. The actual content we are taught should surely be more important than what is the percentage uncertainty in this totally pointless measurement from a totally stupid scenario.

I think they should've integrated those sorts of marks into the actual papers and never had ISAs.
And then we would've been taught how to better prepare for those questions with less ambiguity.

That or make everyone actually sit it in an exam environment. Controlled isn't controlled enough.
Original post by mgill17

I don't know how they don't see how colleges with such exclusively high marks and instantly investigate into it. It really isn't fair.


One of the neighboring schools to ours was actually caught last year. I think someones girlfriend snitched and they all got D's automatically. It made me so happy lol. Plus the teacher got sacked. Apparently he literally put the mark scheme up on the board via a projector
Original post by lucabrasi98
One of the neighboring schools to ours was actually caught last year. I think someones girlfriend snitched and they all got D's automatically. It made me so happy lol. Plus the teacher got sacked. Apparently he literally put the mark scheme up on the board via a projector


How can AQA not note the huge difference in ISA and paper marks...
Original post by Ayaz789
Any predictions on the 6 marker?


transformers imo, which would be nice
Original post by doshea1311
transformers imo, which would be nice


Like will it ask about the energy losses? If it is that i'll be the happiest man in the world!!
Original post by particlestudent
In June 2014 it was 50UMS... do you think it'll be that low this year? :s-smilie:
Same as June 10 as well


I feel like with it being the last year more places will have cheated. To be safe I'd just stick with the same as last year. 50UMS isn't impossible of course but it's a very unlikely thought. I'd say go through all the ISAs since 2010 and find out what the average ums was for 42 marks. The boundaries rarely fluctuate and I don't think this year will be an exception.
Original post by Ayaz789
Like will it ask about the energy losses? If it is that i'll be the happiest man in the world!!


yeah hopefully, i havent seen it come up in a while. either that or shm possibly and working out g.
Original post by lucabrasi98
One of the neighboring schools to ours was actually caught last year. I think someones girlfriend snitched and they all got D's automatically. It made me so happy lol. Plus the teacher got sacked. Apparently he literally put the mark scheme up on the board via a projector


That's something I would totally do. I'm too bitter over grades to not tell everyone ever if someone's cheating. There's a huge difference between our teacher unknowingly trying to guess what might come up and a teacher outright putting a mark scheme up and it's just wrong. I'm glad he got sacked.
Original post by doshea1311
yeah hopefully, i havent seen it come up in a while. either that or shm possibly and working out g.


What do you mean working out g? As a 6 marker? Like what would i write;/

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