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

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What did people put for the unit of flux linkage?
I couldnt remember so I just used the formula BA and wrote unit as Tm^2 (Tesla metre squared).

Reply 4081

Disney0702

Original post by fruity97

I got 15N at first for tension! But I remember changing it towards the end to 12N because I didn't include the weight I think? Stil not sure which is right but they said horizontal so I changed it

I believe i got 12N as well

Reply 4082

Will177

Original post by 000alex

Well the question said 150 ohms in the first part and 300k ohms in the second, It might be a mistake so AQA might remove the mark for intercept?

why would that be a mistake? I thought the whole point in the question was what would happen if you used 300 instead of 150

Reply 4083

Fred Cantoni

Original post by fruity97

I got 15N at first for tension! But I remember changing it towards the end to 12N because I didn't include the weight I think? Stil not sure which is right but they said horizontal so I changed it

Pretty sure cause they said it was horizontal you ignored weight

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Reply 4084

davidharris96

Original post by Will177

That's what I did but I wasn't sure if the initial current changed

I thought it should be twice as low, as V=IR, and V is constant, R increased by x2 so I must decrease by x2

Reply 4085

Willow1.21

Original post by Will177

why would that be a mistake? I thought the whole point in the question was what would happen if you used 300 instead of 150

Because it was Ohms in the first part, kOhms in the second.

Reply 4086

Fred Cantoni

Original post by QueNNch

What did people put for the unit of flux linkage?
I couldnt remember so I just used the formula BA and wrote unit as Tm^2 (Tesla metre squared).

Webber turns

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Reply 4087

000alex

Original post by Will177

why would that be a mistake? I thought the whole point in the question was what would happen if you used 300 instead of 150

300000 instead of 150?

Reply 4088

Will177

Original post by Disney0702

I believe i got 12N as well

I think I just did mv^2/r = T because its horizontal and weight is verticle. Can't remember what value I got

Reply 4089

Hexaneandheels

For the question where we used the graph to calulate things, for the first question I used the graph to show is was 30nC...for the next parts I just used forumulae to calculate, and didn't use the graph, can I still get the marks?

Reply 4090

Greg213

For work done moving the charge, did anyone use W= Q1Q2/4piE0r??

Reply 4091

QueNNch

Original post by Disney0702

I believe i got 12N as well

Well the motion is horizontal so weight is NOT included.

Vertical components and horizontal components are independent (we learned this is AS Unit 2)

Reply 4092

fruity97

What did people put for the iron core coil thing? I just put all I knew about induced emf and what not but I don't think that was even the case?

Reply 4093

Sbarron

Original post by NEWT0N

No time period isn't affected because it only depends on the length of the spring and a simple pendulum is isochronus.

I put the time period stays the same and there is a larger restoring force because the weight is greater at maximum amplitude so the horizontal compoent of weight (restoring force) is larger. But then I went on to say something silly like how this causes a smaller amplitude, but I think it should be a bigger amplitude? My thinking is still a bit cloudy after the exam so I'm hoping someone can clarify this for me! :smile:

Re-read what i put. I didn't say that t was affected by m.... I meant that t wasn't affected and therefore no damping because for damping to occur t would be affected

Reply 4094

Humbers

Original post by fruity97

I got 15N at first for tension! But I remember changing it towards the end to 12N because I didn't include the weight I think? Stil not sure which is right but they said horizontal so I changed it

It was rotated horizontally so weight is perpendicular to centripetal force therefore ignored

T = mv^2/r 0.25 x 8.6^2 / 1.5 = 12.3N

Reply 4095

Will177

Original post by 000alex

300000 instead of 150?

OH wut i didn't even notice the 000000,

Reply 4096

Fred Cantoni

Original post by Hexaneandheels

Yeah I didn't know which was right to do either, guess they'll award marks for both

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Reply 4097

Disney0702

Original post by Mehrdad jafari

Here are my answers. The ones I'm not sure with i have mentioned next to them.

I have failed to take the answer of one of the MC questions. Let me know if you found which one.
I would be very happy if you could correct the ones that are not right :smile:

ImageUploadedByStudent Room1434019809.052314.jpg

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How is the first question acceleration.
Is rate of change of momentum really acceleration?

Reply 4098

DanTheMan358

Original post by Fred Cantoni

I put 2.2x10^10 cause the total number of electrons would be 4.4x10^10 but half would already be on that plate, and the other half moves over from the other plate when they're is a potential difference? Anyone confirm or deny this?

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Ahh i think you may be right.