OCR Physics A G485 - Frontiers of Physics - June 2016

i just hope they don't ask definition on quantum physics. *cough* energy level, absorption spectrum *cough*

Nuclear Reactor

Diagram:

Fuel rods:
-Contain pellets of fissile material such as Uranium or Plutonium

Coolant:
-Can be either gas (carbon dioxide) or liquid (water)
-Used to remove thermal energy produced by the fission reaction in the reactor core.
-This Thermal Energy is used to heat up the water to create high pressure steam to drive the turbines in the generator.

Moderator (graphite):
-Slows down the fast moving neutrons produced in the fission reaction.
It does this by making the neutron collide with the graphite, the collision is inelastic which means that the KE is not conserved hence, slowing the neutrons down.
-Fast-moving neutrons has less chance of being absorbed by the Uranium nucleus than the slow-moving ones.

Controls rods:
-Absorbs neutrons.
-Can be lowered to slow down the fission reaction (cause it will absorb some of the neutrons) Or raised to speed it up.

Anything else?

can anyone link or message me the 2015 paper please

May want to add that control rods are boron. But otherwise it seems pretty good!

screw medical physics. screw them. (except when they include calculations in it, they are normally easy)

May want to add that control rods are boron. But otherwise it seems pretty good!

I just ran through it and did:
age=1/Ho
so you can use the age to fine Ho
then use p=3(Ho)^2/8piG
and i got 9.24x10^-26

just looked at the mark scheme, and i think you might just be reading it wrong because it says: BALD answer is only 2 marks, with working its the full 3 marks i think :P

Hi all.

Can someone walk me through the logic in January 2012 Q9)c)iii)?
The mark scheme simply divided the critical density of the universe by the density of a proton. I got that number but then divided the result by 2, assuming that they would be an equal number of protons and neutrons in the universe.

Are we supposed to just assume the universe only contains protons or did I miss something?

Am I the only one hoping for a lot of 6 markers on medical methods, life cycle of stars, evidence for nuclear charge etc? 🙊

If it's anything like G484 I'm done for. Please actually give us some good physics to spout out. Ain't sat and learned all the definitions and descriptions and theory for nothing.

Stuff from AS is definitively coming up, about energy levels I think and emission and absorption spectrum maybe.

Did they mention this in an examiner's report or are you guessing?

There's no guarantee in space that protons = neutrons in any case, so there isn't necessarily the same number of neutrons as protons here. It's only an estimate based on a general critical density idea.

You're assuming that if p0 is 1x10^-26 kgm^-3 then in 1m^3 you've got 1x10^-26kg of matter mass.

You want to find out the proportion that is protons, so you're dividing that mass (NOT the critical density, the MASS) by the mass of a proton.

If that makes sense?

I hope this helps! I have attached it.