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

1. (Original post by boyyo)
Can anyone explain the differences between electric potential and electrical potential Energy

I get confused between potential and potential energy, I cant get my head around it. Any help appreciated, thanks
Electrical potential is a property of the field and is essentially the potential energy per unit charge. Therefore if the potential tells us the potential energy per unit charge at a point in the field, to get the actual potential energy of a charged species at that point we just multiply the potential by the charge of the charged species
2. (Original post by samb1234)
Electrical potential is a property of the field and is essentially the potential energy per unit charge. Therefore if the potential tells us the potential energy per unit charge at a point in the field, to get the actual potential energy of a charged species at that point we just multiply the potential by the charge of the charged species
(Original post by samb1234)
Electrical potential is a property of the field and is essentially the potential energy per unit charge. Therefore if the potential tells us the potential energy per unit charge at a point in the field, to get the actual potential energy of a charged species at that point we just multiply the potential by the charge of the charged species

Thanks for replying guys, but I still dont quite get it
@samb1234 I sought of get what you mean. But you see in capacitors, when charges build up on opposite plates, why does electric potential energy build up? if you get what I mean
3. (Original post by boyyo)
Thanks for replying guys, but I still dont quite get it
@samb1234 I sought of get what you mean. But you see in capacitors, when charges build up on opposite plates, why does electric potential energy build up? if you get what I mean
I know I am not who you requested to answer, but I was just in the post and I thought I would have a go at mentioning a few things.....

Electric potential is the Electric potential energy divided by the charge of an object which you are working with.

Hence you can just manipulate the above equation to get what ever you want,

And as you are talking about charging a capacitor, you are right that this of course leads to a build up of charge. However we are looking at it for a test charge (Q), as this is a single charge and we are looking at in the context of an electric field.

However what you are talking about is essentially many many of these test charges ( remember a test charge is just a charge placed in an electric field) , being placed one side of the capacitor. So the Key distinction to make here is that the Q which I think you are reffering to is the TOTAL CHARGE , but the Q in electric potential etc.... just represents the charge of a SINGLE OBJECT IN the field.....

Hope this makes sense,

Good luck for the exam.

Will
4. Hey guys does anyone have the Unit 1 PHYA1 2015 paper?, cant seem to find it.
5. (Original post by Billsonbubbles)
I know I am not who you requested to answer, but I was just in the post and I thought I would have a go at mentioning a few things.....

Electric potential is the Electric potential energy divided by the charge of an object which you are working with.

Hence you can just manipulate the above equation to get what ever you want,

And as you are talking about charging a capacitor, you are right that this of course leads to a build up of charge. However we are looking at it for a test charge (Q), as this is a single charge and we are looking at in the context of an electric field.

However what you are talking about is essentially many many of these test charges ( remember a test charge is just a charge placed in an electric field) , being placed one side of the capacitor. So the Key distinction to make here is that the Q which I think you are reffering to is the TOTAL CHARGE , but the Q in electric potential etc.... just represents the charge of a SINGLE OBJECT IN the field.....

Hope this makes sense,

Good luck for the exam.

Will
Ahh ok, thanks for clearing that up, appreciate it
6. (Original post by Billsonbubbles)
Hello I have done some physics videos and other A level videos, could I be added to the list at the start ?

I have done a few quite interesting videos recently, Anyway Brilliant thread ! Thanks for starting this !... I found it really helpful

Many thanks
Funny... I watched your video on EM induction only yesterday and now I find you here. Small world.
7. (Original post by boyyo)
Ahh ok, thanks for clearing that up, appreciate it
Np , I doubt they would ask you to explain the difference,

And besides they wouldn't be as cruel as to confuse you in a question by mixing that test charge thing I mentioned with the total charge ah , so you could just get away with using the equations and not really knowing the difference.

That's what I did for the first half of this year anyway ahah (y)

Will
8. (Original post by Zas_21)
Hey guys does anyone have the Unit 1 PHYA1 2015 paper?, cant seem to find it.
Attached with the mark scheme and examiner's report.
Attached Images
9. AQA-PHYA1-WRE-Jun15.pdf (58.8 KB, 92 views)
10. document.pdf (165.0 KB, 140 views)
11. phy111111.pdf (625.3 KB, 404 views)
12. (Original post by Billsonbubbles)
Np , I doubt they would ask you to explain the difference,

And besides they wouldn't be as cruel as to confuse you in a question by mixing that test charge thing I mentioned with the total charge ah , so you could just get away with using the equations and not really knowing the difference.

That's what I did for the first half of this year anyway ahah (y)

Will
Lol. I've learnt to be prepared for anything thanks to my experience from last year.
Thanks for the help and good luck to you too
13. (Original post by kingaaran)
Attached with the mark scheme and examiner's report.
Do you have the examiner reports on any of the other Physics or Maths papers for AQA?
14. (Original post by TheLifelessRobot)
Do you have the examiner reports on any of the other Physics or Maths papers for AQA?
I have PHYA2, but not any others right this moment. AQA should release them next week, though
15. (Original post by kingaaran)
I have PHYA2, but not any others right this moment. AQA should release them next week, though
16. (Original post by jarjarmonkey)
attached
Attached Images
17. AQA-PHYA2-WRE-Jun15..pdf (65.1 KB, 82 views)
18. document (2).pdf (223.1 KB, 126 views)
19. Can any body explain why the answer to this is B, bit confused
Attached Images

20. (Original post by boyyo)
Can any body explain why the answer to this is B, bit confused
Hello ,

As I think you will be aware the equation for gravitational potential is the work done divided by the mass, and as the work done is also said to be force x distance. This means as X is at a higher point it has covered a greater distance, hence it has a higher gravitational potential.

The reason that they both have the same angular velocity is because the both have the same time period as they are both on the surface of earth. Hence this is proved true as the formula for angular velocity is 2Pi/ Time period.

Hope all of that makes sense

Cheers,

Will
21. (Original post by Billsonbubbles)
Hello ,

As I think you will be aware the equation for gravitational potential is the work done divided by the mass, and as the work done is also said to be force x distance. This means as X is at a higher point it has covered a greater distance, hence it has a higher gravitational potential.

The reason that they both have the same angular velocity is because the both have the same time period as they are both on the surface of earth. Hence this is proved true as the formula for angular velocity is 2Pi/ Time period.

Hope all of that makes sense

Cheers,

Will
Hi will, thanks for replying again!

I understand everything you said, but when i saw the question, I first thought, gravitational potential, v = GM/r. So if X is at a higher point, r for x than for Y. V is inversely proportional to r so V for X is smaller. Which isnt right as its not an option here. How did you know to use w=fs straight away??

Also, you said, bot x and y are on surface of earth, but x is higher than y, so would that not effect it since w=v/r, or am i completly off

Appreciate the help btw
22. (Original post by boyyo)
Hi will, thanks for replying again!

I understand everything you said, but when i saw the question, I first thought, gravitational potential, v = GM/r. So if X is at a higher point, r for x than for Y. V is inversely proportional to r so V for X is smaller. Which isnt right as its not an option here. How did you know to use w=fs straight away??

Also, you said, bot x and y are on surface of earth, but x is higher than y, so would that not effect it since w=v/r, or am i completly off

Appreciate the help btw
Gravitational potential is technically a vector quantity and in reality if you take outwards from the centre as positive v=-Gm/r, its just that normally yiu see the magnitude discussed. Therefore if the radius is bigger, the potential is less negative so is greater
23. [QUOTE=boyyo;64540505]Hi will, thanks for replying again!

I understand everything you said, but when i saw the question, I first thought, gravitational potential, v = GM/r. So if X is at a higher point, r for x than for Y. V is inversely proportional to r so V for X is smaller. Which isnt right as its not an option here. How did you know to use w=fs straight away??

Also, you said, bot x and y are on surface of earth, but x is higher than y, so would that not effect it since w=v/r, or am i completly off

Appreciate the help btw [/QUOTE

I dont really know, it just came to me when I saw the question... it might not be 100% correct, but I dont see why my method wouldn't be.... I dont think the equation you use works for something on the surface of earth,,, I am not 100% on that though.

sorry I don't know exactly what you mean for the second paragraph ... you are not talking about why the angular velocity is the same are you ?

No worries, sorry I cant be of much help.... at the end of the day it is just one question,,, so don't worry to much if you dont get it ... i'll ask my teacher for you tomorrow and see what she says

Ill post on here when she gets back to me , as I cant be 100% on what I have said.

Will
24. [QUOTE=Billsonbubbles;64542517]
(Original post by boyyo)
Hi will, thanks for replying again!

I understand everything you said, but when i saw the question, I first thought, gravitational potential, v = GM/r. So if X is at a higher point, r for x than for Y. V is inversely proportional to r so V for X is smaller. Which isnt right as its not an option here. How did you know to use w=fs straight away??

Also, you said, bot x and y are on surface of earth, but x is higher than y, so would that not effect it since w=v/r, or am i completly off

Appreciate the help btw [/QUOTE

I dont really know, it just came to me when I saw the question... it might not be 100% correct, but I dont see why my method wouldn't be.... I dont think the equation you use works for something on the surface of earth,,, I am not 100% on that though.

sorry I don't know exactly what you mean for the second paragraph ... you are not talking about why the angular velocity is the same are you ?

No worries, sorry I cant be of much help.... at the end of the day it is just one question,,, so don't worry to much if you dont get it ... i'll ask my teacher for you tomorrow and see what she says

Ill post on here when she gets back to me , as I cant be 100% on what I have said.

Will
thank you I really appreciate that. I didnt get what you ment about the angular velocit bit at first but I undertand it now, thanks
25. [QUOTE=boyyo;64555787]
(Original post by Billsonbubbles)

thank you I really appreciate that. I didnt get what you ment about the angular velocit bit at first but I undertand it now, thanks
Ahah no worries

Just to be clear though you can calculate angular velocity = 2Pi / T

Where T is the time period and as they both have the same time period they both have the same angular velocity.

Your equation of V being = 2Pi x radius / Time period is the speed on the perimeter is NOT ANGULAR SPEED.

Sorry to put that in caps .... it was just so it is made clearer ,

and my teacher agrees with on my points... so it should all be correct.

Good luck again for the exam ,

Will

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