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<a https://www.thestudentroom.co.uk/showthread.php?t=7467335'> Year 12s: what will be the first way you research your future options? >>

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

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Original post by TashJacobs
I managed to get the paper today, would anyone like me to post pictures of any pages/questions?

Would be great if you could upload the multi choice part! :smile:
Original post by TashJacobs
I managed to get the paper today, would anyone like me to post pictures of any pages/questions?


Possible to take pictures of the Multiple Choice Section? Kind of find it hard to remember which answer I put down when I do not know the other three options that were available (trying to check what I put down against the mark scheme). Thanks!
Original post by Salt and Peppa
Possible to take pictures of the Multiple Choice Section? Kind of find it hard to remember which answer I put down when I do not know the other three options that were available (trying to check what I put down against the mark scheme). Thanks!


He did upload them, if the link is still available


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Reply 4923
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CD223
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Original post by Vincent Song
shouldnt it be minus?


I suppose it should yes, although I'm not sure whether that will be a marking point.


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Original post by CD223
I suppose it should yes, although I'm not sure whether that will be a marking point.


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I used the electric field strength equation and I substituted the value of Q ,which was negative, in that equation and then I got -1560. :smile:
Original post by Vincent Song
I used the electric field strength equation and I substituted the value of Q ,which was negative, in that equation and then I got -1560. :smile:


Damn, which charge did you use??

Edit: sorry, did you use the field strength for a point charge?

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(edited 8 years ago)
Original post by Mehrdad jafari
Damn, which charge did you use??

Edit: sorry, did you use the field strength for a point charge?

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-27.8nC if that helps.
Reply 4927
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CD223
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How fussy are examiners on minus signs? Neither my electric field strength nor work done was negative :/


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Original post by CD223
How fussy are examiners on minus signs? Neither my electric field strength nor work done was negative :/


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I don't think if mine was either :frown:. If in the previous past papers the minus sign is in a bracket then the mark is not deducted


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(edited 8 years ago)
Original post by Vincent Song
-27.8nC if that helps.


Sorry, where did you get that?
Edit: i got it, but i used the electric field formula for a point charge which gave me a different answer

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Original post by CD223
How fussy are examiners on minus signs? Neither my electric field strength nor work done was negative :/


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The work done should be positive I think.
Reply 4931
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Original post by Vincent Song
The work done should be positive I think.


Oh really? I'm still unsure. To be honest I guess the numerical answer being right is the main thing.


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The work done should be positive because it was the work done on a positive (60nC) charge
Original post by Mehrdad jafari
Sorry, where did you get that?
Edit: i got it, but i used the electric field formula for a point charge which gave me a different answer

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.
I got that value in 2c(i). Which formula? Is it E=Q/(4pie sth r^2)?
But if you use it for a point charge, how to u know which charge to use because they didnt specify whether they were asking it E for 30nc or 60nc..... I personally found the whole electric potential calculations so misleading/unclear..
Original post by Vincent Song
The work done should be positive I think.


Thats true. The work done is positive. Since the potential is negative it means that the charge causing the potential is negative. Therefore for a positive charge to be moved from a less distance to a further distance from the negative charge, work "has to" be done on the positive charge because they are attracted. Though i was not conscious of this reasoning during the exam


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Original post by dmp1188
But if you use it for a point charge, how to u know which charge to use because they didnt specify whether they were asking it E for 30nc or 60nc..... I personally found the whole electric potential calculations so misleading/unclear..


You have to use the charge causing the potential, that is 30nc


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Original post by sam_97
The work done should be positive because it was the work done on a positive (60nC) charge


Not necessarily. If the positive charge was moved from a greater distance to a closer distance to the negative charge then the work done would be negative


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Original post by Vincent Song
.
I got that value in 2c(i). Which formula? Is it E=Q/(4pie sth r^2)?


Yeah, i think


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Original post by Mehrdad jafari
Not necessarily. If the positive charge was moved from a greater distance to a closer distance to the negative charge then the work done would be negative


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Oh yeah good point!

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