# AQA PHYA4 ~ 13th June 2013 ~ A2 Physics Watch

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#1061

(Original post by

Can anyone else confirm that the y axis was change in flux linkage?

and i'm going to school tomorrow, i'll ask my teacher if they have a copy of the paper :P

**MisterE1**)Can anyone else confirm that the y axis was change in flux linkage?

and i'm going to school tomorrow, i'll ask my teacher if they have a copy of the paper :P

emf is rate of change of flux linkage

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#1062

(Original post by

that diagram is showing a positive cosine graph for flux

and apparently the flux graph in that exam was negative

**Jack93o**)that diagram is showing a positive cosine graph for flux

and apparently the flux graph in that exam was negative

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#1063

one was showing how flux changes over time, and this graph was minus cosine (unless someone remembers it was something else?)

and the second graph below was the one which we had to use to draw how emf varies

the CGP flux graph posted robmarkey shows a

**positive**cosine graph, and it shows a positive sine graph for emf

so what I was saying is that the graphs in the CGP book is not exactly the same as in our exam

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#1064

(Original post by

IT definitely did not say change in flux linkage, if it did the gradient of the line would not represent the emf, but the change in change of flux linkage. No one plots a graph of change in flux linkage against time lol

EDIT: actually that is the same as emf against time but that's the graph they asked you to draw so they definitely wouldn't print it in the paper in the first place

**marcolliwright**)IT definitely did not say change in flux linkage, if it did the gradient of the line would not represent the emf, but the change in change of flux linkage. No one plots a graph of change in flux linkage against time lol

EDIT: actually that is the same as emf against time but that's the graph they asked you to draw so they definitely wouldn't print it in the paper in the first place

emf is the rate of change of flux linkage

so the gradient gave the emf

i dont know i might be wrong but thats what i can remember we'll see when someone gets hold of the paper

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#1065

(Original post by

Lmao I actually thoughht that when i turned the page it would be a 6 marker All in all not bad paper could have been harder. wbu?

**Dirtybit**)Lmao I actually thoughht that when i turned the page it would be a 6 marker All in all not bad paper could have been harder. wbu?

Anyway. Just trying to focus on unit 5 now, but the astrophysics option just makes me sleepy!

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#1066

(Original post by

Hi guys, just had one question about the exam which has been puzzling me. I may have incorrectly read the question, but correct me if I'm wrong:

In the question regarding the parallel discs where it asked the time between consecutive sparks if the capacitance were to be increased. I understand the logic behind thinking that if capacitance goes up, then the time constant goes up, therefore the time between sparks increases. However i specifically remember the question telling us that the current (rate of flow of charge) was constant, hence the system would not be an exponential increase of charge but rather a constant increase in charge. Therefore for a greater capacitance, a smaller charge must be stored to achieve the required 30'000V, therefore the time between sparks would in fact be shorter. Please explain to me if my reasoning is correct?

I specifically remember asking myself whether this was a trick question and gave it an extra thought.

**smatts**)Hi guys, just had one question about the exam which has been puzzling me. I may have incorrectly read the question, but correct me if I'm wrong:

In the question regarding the parallel discs where it asked the time between consecutive sparks if the capacitance were to be increased. I understand the logic behind thinking that if capacitance goes up, then the time constant goes up, therefore the time between sparks increases. However i specifically remember the question telling us that the current (rate of flow of charge) was constant, hence the system would not be an exponential increase of charge but rather a constant increase in charge. Therefore for a greater capacitance, a smaller charge must be stored to achieve the required 30'000V, therefore the time between sparks would in fact be shorter. Please explain to me if my reasoning is correct?

I specifically remember asking myself whether this was a trick question and gave it an extra thought.

Increase C, increase Q, not a decrease!

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#1067

Also why is the magnetic field on page 114 (nelson thornes, AQA) directed into the cyclotron?

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#1068

Guys and girls...since we're still debating the +/- sine curve....can we also debate that multiple choice ratio question where most people got 2/3 but people are saying the answer is 1/3? Is it concrete that the answer is 1/3?

I'm just clutching on to straws here really.. Should have f'ing started revising earlier.

I'm just clutching on to straws here really.. Should have f'ing started revising earlier.

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#1069

(Original post by

in the exam, there were two graphs

one was showing how flux changes over time, and this graph was minus cosine (unless someone remembers it was something else?)

and the second graph below was the one which we had to use to draw how emf varies

the CGP flux graph posted robmarkey shows a

so what I was saying is that the graphs in the CGP book is not exactly the same as in our exam

**Jack93o**)in the exam, there were two graphs

one was showing how flux changes over time, and this graph was minus cosine (unless someone remembers it was something else?)

and the second graph below was the one which we had to use to draw how emf varies

the CGP flux graph posted robmarkey shows a

**positive**cosine graph, and it shows a positive sine graph for emfso what I was saying is that the graphs in the CGP book is not exactly the same as in our exam

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#1070

(Original post by

from what i can remember the y-axis was change in flux linkage

emf is the rate of change of flux linkage

so the gradient gave the emf

i dont know i might be wrong but thats what i can remember we'll see when someone gets hold of the paper

**saba146**)from what i can remember the y-axis was change in flux linkage

emf is the rate of change of flux linkage

so the gradient gave the emf

i dont know i might be wrong but thats what i can remember we'll see when someone gets hold of the paper

**literally**say

**"change in flux linkage"**however that graph represented how the flux linkage is changing over time.

If the y axis did actually say

**change in flux linkage**(which it didn't) then it would be the same as the emf-time graph. What the y-axis itself represented was the flux linkage. It was the whole graph which showed the change in flux linkage.

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#1071

(Original post by

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**cooldudeman**)**Yh so the answer to ours is -sin**. I thought you were saying it isn'tPosted from TSR Mobile

at the start I thought it was positive, but it now seems like it should've been negative

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#1072

(Original post by

Guys and girls...since we're still debating the +/- sine curve....can we also debate that multiple choice ratio question where most people got 2/3 but people are saying the answer is 1/3? Is it concrete that the answer is 1/3?

I'm just clutching on to straws here really.. Should have f'ing started revising earlier.

**kingm**)Guys and girls...since we're still debating the +/- sine curve....can we also debate that multiple choice ratio question where most people got 2/3 but people are saying the answer is 1/3? Is it concrete that the answer is 1/3?

I'm just clutching on to straws here really.. Should have f'ing started revising earlier.

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#1073

im hopingg.. the grade boundaries are similar to the took in jan... man.. physics is just too hard

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#1074

(Original post by

im hopingg.. the grade boundaries are similar to the took in jan... man.. physics is just too hard

**xoxoxoxoxox**)im hopingg.. the grade boundaries are similar to the took in jan... man.. physics is just too hard

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#1075

The graph was negative....yea I did say change In flux I've got the paper here.

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#1076

(Original post by

The graph was negative....yea I did say change In flux I've got the paper here.

**Robmarkey**)The graph was negative....yea I did say change In flux I've got the paper here.

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#1077

**Robmarkey**)

The graph was negative....yea I did say change In flux I've got the paper here.

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#1078

(Original post by

If you've got the paper then upload it. Not like anyone's been asking for it you know..

**MSI_10**)If you've got the paper then upload it. Not like anyone's been asking for it you know..

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#1079

(Original post by

I'm filling in the answers but I got to check them so there not uploaded with silly mistakes, it will be up first thing tomorrow section B anyway.but I can assure you that the graph is negative!

**Robmarkey**)I'm filling in the answers but I got to check them so there not uploaded with silly mistakes, it will be up first thing tomorrow section B anyway.but I can assure you that the graph is negative!

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#1080

**Robmarkey**)

I'm filling in the answers but I got to check them so there not uploaded with silly mistakes, it will be up first thing tomorrow section B anyway.but I can assure you that the graph is negative!

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