OCR Physics A - G485: Fields, Particles &amp; Frontiers of Physics - June 2012

What is everyone predicting the long essay questions are going to be in this paper. Which ones haven't? come up for a while?

I reckon the test is going to be

1. Capacitors
2. Electric fields (point charges)
3. Electric fields (potential gradient
4. AC generator/Change in magnetic flux linkage
5. BQv=MV^2/r (Mass spec)
6. Xrays
7. Evolution of the Universe
8. Ultrasound
9. MRI
10. Nuclear Reactor and binding energy

Reply 582

I think in some form or other the evolution of the universe will come up, possibly as an 6/8 mark question. It has never come up on a paper and officially they have to cover all the specification topics in three years.

Reply 583

Mathlete 4 the win

Original post by Picture~Perfect

officially they have to cover all the specification topics in three years.

Where did you get this from? For OCR maths I have known something (proof by contradiction for C3) to be on the specification and to have never come up and those papers have been going since like 2005 or something.

Reply 584

OllyHV

Original post by Picture~Perfect

I think in some form or other the evolution of the universe will come up, possibly as an 6/8 mark question. It has never come up on a paper and officially they have to cover all the specification topics in three years.

Hope not, there is no way I'm going to be able to learn all this.

T=0s: all the matter in the universe concentrated at one infinitely dense, infinitely hot point known as a singularity
-T=10-43s: all four fundamental forces are unified, rapid expansion takes place
-T=10-34s: gravitational force separates from the other forces, primordial quark soup formed with photons
-T=10-16s: strong nuclear force separates, leptons form from photons.
-T=10-3s: weak nuclear and electromagnetic separate, quarks can exist in protons and neutrons. Ratio of protons to neutrons is 4:1
-T=100s: Helium and lithium nuclei formed, but temperature is becoming too cool for further fusion to occur, matter is currently in a plasma phase where protons are not attached to electrons as temperature is too high.
-T=100 000 years: universe is cool enough for atoms to be formed and becomes transparent as photons are free to travel. CMB is formed.
-T= 1 million years: overall structure of the universe formed.
-T= 1 billion years: universe gains more structure, heavy elements formed from gravitational collapse
-T=13 billion years: present day, ratio of protons: neutrons is still 4:1.

Reply 585

Original post by 4 Mathlete the win

Where did you get this from? For OCR maths I have known something (proof by contradiction for C3) to be on the specification and to have never come up and those papers have been going since like 2005 or something.

As I said ''officially'' that is supposed to be the case, its true for all exams. I realise that in reality some topics don't actually get covered buts its unusual.

Original post by OllyHV

Hope not, there is no way I'm going to be able to learn all this.

You only have to learn what happens qualitatively, you don't need to know times or temperatures. If you're struggling check out the first post of this thread, I've made a pdf document that simplifies the evolution of the universe.

Reply 586

chemengmeng

Original post by OllyHV

Hope not, there is no way I'm going to be able to learn all this.

On the specification it says "describe qualitatively the evolution of the universe..."

So you don't need to know the numbers

Reply 587

Jukeboxing

8

Original post by 21Grapes

anyone? :/ this is on the spec but i haven't seen a question on it yet

This was posted from The Student Room's Android App on my GT-I9100

Goto first page and download my pdf on nuclear physics, i've explained it in bullet points.

Reply 588

ReTurd

Can someone ask me questions? And i will in return.

Reply 589

chemengmeng

Original post by ReTurd

Can someone ask me questions? And i will in return.

Give evidence that supports the big bang theory

Reply 590

JuxtaposedJames

Original post by chemengmeng

Give evidence that supports the big bang theory

Evidence of cosmic microwave background radiation at 2.3K
More helium in universe than expected
Red shifted spectra
Galaxies moving away from each other (must have come from a point)
Further way the faster the speed of recession for a galaxy

Reply 591

21Grapes

10

Original post by hyphen

x

Original post by Picture~Perfect

x

Original post by Jukeboxing

Goto first page and download my pdf on nuclear physics, i've explained it in bullet points.

Thanks. I understand most of it now but im still unsure about what ionisation actually is? how do alpha particles cause ionisation? (or do we not need to know the details?). Also, why is 241Am used if the half life is way way longer than the anticipated use of the alarm?
Sorry for all the questions but i really appreciate it :biggrin:

Reply 592

hyphen

Original post by 21Grapes

Thanks. I understand most of it now but im still unsure about what ionisation actually is? how do alpha particles cause ionisation? (or do we not need to know the details?). Also, why is 241Am used if the half life is way way longer than the anticipated use of the alarm?
Sorry for all the questions but i really appreciate it :biggrin:

ionisation is bascially when an alpha particle knocks an electron out of the atom so the atom becomes positively charged, an ion. they (Alpha particles) have a lot of energy and are large so collide with air molecules and pull electrons off it since the alpha particles are positive and electrons are negative but we dont really need to know that i dont think, and im not sure about that, maybe it has the shortest half life they could find? :tongue:

Reply 593

Toshiya

Original post by 21Grapes

Also, why is 241Am used if the half life is way way longer than the anticipated use of the alarm?

Well I've not seen it on a paper or in the textbook, but my guess would be that this way, the Am won't decay to the point where the alarm is ineffective at any point in its lifetime. :smile:

Reply 594

Original post by 21Grapes

Thanks. I understand most of it now but im still unsure about what ionisation actually is? how do alpha particles cause ionisation? (or do we not need to know the details?). Also, why is 241Am used if the half life is way way longer than the anticipated use of the alarm?
Sorry for all the questions but i really appreciate it :biggrin:

You don't really need to understand the details.
Honestly I don't know why americium is used, the long half life is probably to ensure that the sample doesn't completely decay during the lifetime of the detector. It doesn't actually matter, you're over thinking this. You just need to explain the basic concept of a smoke detector for this exam.

(edited 11 years ago)

Reply 595

marcusrc

Can someone please explain mass spectrometers for a 4-6 mark question. I've read about it in both the books I have and I still don't understand its main components. Please :smile:

Reply 596

king0vdarkness

2

Original post by marcusrc

Can someone please explain mass spectrometers for a 4-6 mark question. I've read about it in both the books I have and I still don't understand its main components. Please :smile:

Charged particle accelerated by electric field and deflected by magnetic field. Then angle of deflection measured by computer and placed against known ions and the sample is therefore identified. Hope this helps! :smile:

Reply 597

Original post by marcusrc

Can someone please explain mass spectrometers for a 4-6 mark question. I've read about it in both the books I have and I still don't understand its main components. Please :smile:

A mass spectrometer determines the mass of charged ions and their relative abundance.

A velocity selector is used to isolate ions of a particular speed. A uniform magnetic field is used to deflect the charge ions in a circular path in an educated chamber. A movable detector or photographic film is used to determine the radius of the path and the relative abundance of the ions.

Once the ions are in the magnetic field they travel in a circular path and hence experience a centripetal force.

BQv = mv^2/r

r= mv/BQ

The radius is directly proportional to the mass of the charged ion.

(edited 11 years ago)

Reply 598

king0vdarkness

2

Quick question for Larmor Frequency (f) do we need to know the equation
f= (gyromagnetic ratio*magnetic flux density of external field)/2π ? any help would be much appreciated :wink:

thanks in advance!

Reply 599