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

1. (Original post by marioman)
You are calculating the electric potential rather than the electric potential energy.
Ah I see now, thanks I just realised that the answers are repeated as well
2. Does anyone know all the practicals they could ask about in unit 4? And have 6 mark answers for all of them including diagrams?
3. I don't get the last one...surely it should be the angle between the NORMAL to the plane of the coil and the magnetic field?
Attached Images

4. (Original post by Nikhilm)
I don't get the last one...surely it should be the angle between the NORMAL to the plane of the coil and the magnetic field?
Not really, an angle of zero relative to the normal could be measured as an angle of 90 from the plane.
5. (Original post by jarjarmonkey)
Does anyone know all the practicals they could ask about in unit 4? And have 6 mark answers for all of them including diagrams?
SHM pendulum, SHM springs and capacitor charging is all I can think of?
6. (Original post by rich1334)
Not really, an angle of zero relative to the normal could be measured as an angle of 90 from the plane.
True. How would an increase in the angle between plane of coil and field give a larger emf though? Because an increase could be anything, e.g. 35 degrees, and hence would always be less than 1 for costheta or sintheta
7. (Original post by particlestudent)
Nope, that's incorrect.

It spins 2(pi) radians in 24 hours so in one hour it would spin 1/12 (pi). Divide the 2(pi) by 24 to get it for one hour.

1/12 pi is around 0.262 radians.

Thanks once again
. Good luck although you don't need it, as you seem to be ready for this exam
8. (Original post by kother2015)
Thanks once again
. Good luck although you don't need it, as you seem to be ready for this exam
Thanks, I feel ready, but not ready at the same time . I have no idea what to expect on this exam, I just hope section B is okay...
9. Hey everyone!

I'm feeling averagely confident on unit 4 for monday (relying on a good multiple choice to boost my grade chances up) I just could really use some help on some minor things that I can't get my head around and if anyone could explain them it would be much appreciated

1) How does a transformer work? (I know this was a six marker/ and asked similarly with the ring going down the pole) but electromagnetic induction is my weakest area so an explanation about these two things such as the steps involved would be an amazing amount of help!

2) Can anyone explain the effects/how we know what polarity of the coil is north/south? for example when you put a magnet in north end first into a coil, how do we know whether the flux linkage increases/decreases? I struggle with determining the polarity of the magnet with the coil story.

Basically, if I had to rank my priority it would be how a transformer works, but aside from that anything anyone has to further help explain electromagnetic induction would be amazing as thats my weakest topic which I don't feel very good on. Aside from that

I wish everyone on here the best of luck for Monday morning and I'm sure we'll nail it (as long as AQA aren't going to mess up this paper)
10. http://filestore.aqa.org.uk/subjects...W-QP-JUN11.PDF

4c

i dont really get why its upwards force and why 4b is into plane for field either, is force always opposite the field?
11. http://filestore.aqa.org.uk/subjects...W-QP-JAN12.PDF
Q17? Someone explain it to me please?
12. (Original post by liverpool2044)
http://filestore.aqa.org.uk/subjects...W-QP-JUN11.PDF

4c

i dont really get why its upwards force and why 4b is into plane for field either, is force always opposite the field?
Use the left hand rule and you should see that for your thumb to stick up (force), your forefinger will be pointing into the paper for that to happen (ion moving to the right).

For C, BQv=EQ (from the previous part), if the velocity goes higher than v, then the magnetic force will be stronger than the electrostatic force. So they would move upwards as that's where the magnetic force is pushing them.
13. (Original post by particlestudent)
Use the left hand rule and you should see that for your thumb to stick up (force), your forefinger will be pointing into the paper for that to happen (ion moving to the right).

For C, BQv=EQ (from the previous part), if the velocity goes higher than v, then the magnetic force will be stronger than the electrostatic force. So they would move upwards as that's where the magnetic force is pushing them.
ah great does it not matter the type of charge for left hand rule? ive seen questions regarding electrons and protons with varied answers
14. (Original post by Ayaz789)
http://filestore.aqa.org.uk/subjects...W-QP-JAN12.PDF
Q17? Someone explain it to me please?
V=QC

6=600(uC) * C

If the charge increases by 50%, it will essentially be 900uC. So it's gotten 1.5 times bigger.
So 1.5*6 will then give you your new voltage of 9.0V.
15. (Original post by Ayaz789)
http://filestore.aqa.org.uk/subjects...W-QP-JAN12.PDF
Q17? Someone explain it to me please?
When charged to a p.d. of 6.0 V, charge stored is 600 μC. So, using C = Q/V, capacitance = 600*10^(-6)/6 = 0.0001 F.

Now, when the charge stored increases by 50%, new charge stored = 600*1.5 = 900 μC.

The capacitance stays constant, so the p.d. is now V = Q/C = 900*10^(-6)/0.0001 = 9.0 V.
16. (Original post by liverpool2044)
ah great does it not matter the type of charge for left hand rule? ive seen questions regarding electrons and protons with varied answers
It does matter, this one was a positive ion though so you can use the left hand rule without any alterations. E.g. An electron moving vertically down has to be treated as a positive charge moving vertically up.
17. (Original post by particlestudent)
V=QC

6=600(uC) * C

If the charge increases by 50%, it will essentially be 900uC. So it's gotten 1.5 times bigger.
So 1.5*6 will then give you your new voltage of 9.0V.
But V doesnt= QC , your working is right though Thanks
18. (Original post by jarjarmonkey)
Does anyone know all the practicals they could ask about in unit 4? And have 6 mark answers for all of them including diagrams?
here are six markers with the answers for unit 4, that's not all of them but my physics teacher sent me them so I hope this helps
Attached Files
19. A2 Extended Writing - Lesson 1 - Unit 4 - Questions 2.0.docx (68.4 KB, 214 views)
20. A2 Extended Writing - Lesson 1 - Unit 4 - Answers 2.0.docx (33.9 KB, 136 views)
21. (Original post by Ayaz789)
But V doesnt= QC , your working is right though Thanks
Sorry my bad I'm half dead, Q/C- should still give you the same proportion ....
luckily
22. (Original post by particlestudent)
It does matter, this one was a positive ion though so you can use the left hand rule without any alterations. E.g. An electron moving vertically down has to be treated as a positive charge moving vertically up.
does this apply to electric and magnetic? does it vary in a current aswell because that can just use the left hand rule to find the motion of the electrons

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