AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread]

OP

Original post by Mehrdad jafari

It's june 2002 paper, as it's written in the web link :smile:

I see!

Original post by gcsestuff

Thanks makes sense! Another good case of not reading the question properly. And unit 4 in the old syllabus included nuclear energy, some quite good questions in there

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Thanks man - would you mind linking me to that website? Might have a go at a few.

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Reply 1141

gcsestuff

Original post by frankiejayx

Would anyone mind explaining the concept of critical mass to me? For the fuel rods

It's the minimum amount of mass required for fission to keep occurring, I think it's something to do with the proportion of neutrons on the surface, if you're left with too few the nuclei aren't heavy enough to split. I think I'm right but I'm not 100% either. I'll take a photo of my old text book when I'm home

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Reply 1142

gcsestuff

Original post by CD223

I see!

Thanks man - would you mind linking me to that website? Might have a go at a few.

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Just google tom Reds blog. He has all the old papers for all units. He has a navigation bar at the top of his page.

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Reply 1143

OP

Original post by frankiejayx

Would anyone mind explaining the concept of critical mass to me? For the fuel rods

Critical mass is the mass of fuel needed for a chain reaction to occur. In other words, the mass required for one neutron released from each fission event to cause at least one other fission reaction.

Below the critical mass, on average one fission event causes less than one more fission event (sounds stupid but if you imagine a large quantity of atoms it makes more sense).

At the critical mass, one fission event can lead to just one other fission event.

Above the critical mass, one fission event can go on to cause several more fission events.

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Reply 1144

OP

Original post by gcsestuff

Just google tom Reds blog. He has all the old papers for all units. He has a navigation bar at the top of his page.

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Brilliant thanks :smile:

Reply 1145

frankiejayx

Original post by gcsestuff

It's the minimum amount of mass required for fission to keep occurring, I think it's something to do with the proportion of neutrons on the surface, if you're left with too few the nuclei aren't heavy enough to split. I think I'm right but I'm not 100% either. I'll take a photo of my old text book when I'm home

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Okay Thank you :smile:

Reply 1146

frankiejayx

Original post by CD223

Critical mass is the mass of fuel needed for a chain reaction to occur. In other words, the mass required for one neutron released from each fission event to cause at least one other fission reaction.

Below the critical mass, on average one fission event causes less than one more fission event (sounds stupid but if you imagine a large quantity of atoms it makes more sense).

At the critical mass, one fission event can lead to just one other fission event.

Above the critical mass, one fission event can go on to cause several more fission events.

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Thanks!

Reply 1147

OP

Original post by frankiejayx

Thanks!

No problem :smile:

Reply 1148

gcsestuff

Original post by CD223

No problem :smile:

https://m.youtube.com/watch?v=T5qmCkSU7CU

I watched this set of videos, I thought he was quite good :smile:

Reply 1149

OP

Original post by gcsestuff

https://m.youtube.com/watch?v=T5qmCkSU7CU

I watched this set of videos, I thought he was quite good :smile:

Ah that's cool :smile:

Reply 1150

AR_95

21

are we expected to be able to derive the equations for the ideal gas laws and kinetic theory?

Reply 1151

Master Sam

1

Hi does anyone know why there are no PHYA5 papers for the January set of papers in all the years on the AQA website? Theres papers for PHYA4 for Jan and June but for PHYA5 its only June?

Reply 1152

dominicwild

6

I don't get why they did

mc(30 - T_f)

on the mark scheme. I get why they did

mc(T_f - 3)

As that's the difference between before and after temperature? At least I think.

Reply 1153

Lau14

11

Original post by Master Sam

Hi does anyone know why there are no PHYA5 papers for the January set of papers in all the years on the AQA website? Theres papers for PHYA4 for Jan and June but for PHYA5 its only June?

PHYA5 papers were only sat in summer, because it's the second unit of the year the idea was do phya4 for january then do phya5 for june :/ it's a pain now when we've hardly got any past papers!

Reply 1154

OP

Original post by AR_95

are we expected to be able to derive the equations for the ideal gas laws and kinetic theory?

Yes, it's in the spec.

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Reply 1155

OP