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

I think the current flowed from Y to C2 even though the electron flow was in the reverse direction.


Posted from TSR Mobile

All three options make sense to me. I don't dismiss any of them because all arguments have convincingly "correct" supporting evidence.

I wasn't sure if it meant the instant that V2 was at a max or just after.


Posted from TSR Mobile

Lol I'm now more confused than I was in the exam. I'm pretty sure I'm wrong. It's an equal split of opinion amongst my friends and classmates.

Once you have the MS it will be interesting to see how it turns out. I can't make my mind up which I believe - I certainly don't think what I put was correct reasoning, even if I did tick the right box by fluke.


Posted from TSR Mobile

Yeah, even I didn't know what i was doing during the exam and i realised it just a while ago


Posted from TSR Mobile

and unit four grade boundaries

Haha. How come you have access to you MS by the way - do your teachers let you?

Wish mine did


Posted from TSR Mobile

I can understand you. In such a case the answer is already suggested to you, you only need to explain that. Which part of the first question did you have difficulty with?


Posted from TSR Mobile

No, a friend of mine has access to them and so he gives me


Posted from TSR Mobile

$[br]E =\dfrac{1}{2} CV^2[br]$

As the capacitor stores half the energy supplied by the battery.

$[br]P =\dfrac{\Delta E}{\Delta t}[br]$

$[br]\Rightarrow P=\dfrac{CV^2}{2 \Delta t}[br]$

That's cool - it'd be interesting to see what the answers to the obscure questions were. Like how a thinner match stick would change the graph haha.


Posted from TSR Mobile

Hmm that definitely makes sense, but then what is wrong with my derivation of P=CV^2/t?

Yeah true. I think there was a similar question to that in EMPA june 14. I wrote the gradient is unaffected and only the Y intercept increases. And you?


Posted from TSR Mobile

The capacitor stores half the energy of the supply. Your derivation assumes all the energy from the supply is stored by the capacitor, which isn't the case.

Again, not confident in my answer. I said the gradient of $y$ against $\frac{1}{x}$ would increase.

That paper didn't go well in my opinion, although there's not much I can do now.


Posted from TSR Mobile

Ah of course, thank you!

Neither am i. What was x again, sorry?


Posted from TSR Mobile

What did everyone put for the last question on the EMPA?

What did everyone put for the last question on the EMPA?