June 2011 G485-Fields, Particles and Frontiers of Physics

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I'm a bit nervous regarding this exam. I have only covered half the specification atm, bec of starting revision late and other exams. I need an A to get into my first choice and i'm also taking G484 as i'm doing A2 in one year. :L

Reply 101

FristyKino

Original post by apo1324

Maybe im just being thick but A2 is done in 1 year? :confused:

Reply 102

contrarymary

i hate this module! there's sooo much to know and whatever i try it never seems to stick in my mind!!

but those revision notes are superb, thanks to whoever posted them!!

Reply 103

CharleyChester

I need 65 ums on this exam to get a B overall. Still stressing major league though, nothing i revise sticks :/

Reply 104

jamedz

Really hope this exam is alright after the ecology biology, and apparently the OCR chemistry was horrible. Hoping ours is sort of the 3rd exam lucky :P

Reply 105

Ralphus J

Original post by ChoYunEL

A Mass Spectrometry uses the principle of f = (m*v^2)/r
The Spectrometer will project/accelerate a substance of unknown material/substances through a magnetic and/or Electric field.
Force/Velocity^squared = Mass/Radius

Since you cannot change the mass of an material, a detector/collector picks up where the material is using the radius it has traveled through the magnetic field.

There are two types of mass spectrometer as far as I understand..
One which only allow one particular substance through a gap (using electric fields to stop additional ions)
And ones which has several detectors, without an electric field, which collects certain irons.

Please correct me if I am wrong.

Thanks alot!

Reply 106

Ralphus J

Is there any chance i could have some help with Transformers, stepping up and down, i dont really get it and the equations, it would be very much appreciated.
Thanks

Reply 107

Nirgilis

Original post by jamedz

Really hope this exam is alright after the ecology biology, and apparently the OCR chemistry was horrible. Hoping ours is sort of the 3rd exam lucky :P

.. The Ecology exam was hilariously narrow :rofl:

.. Lucky I'm only on OCR for Biology and Physics :yep:

Funniest thing to come out of the Ecology fiasco: :rofl2:

Spoiler

(edited 12 years ago)

Reply 108

Ralphus J

LOL XD, theres a Facebook group called "those against the F215 paper" OCR have released a statement which is on the group.

Anyway... do we need to know about emf graphs, i know there on the legacy papers, is it on our syllabus?

Reply 109

Oh my Ms. Coffey

I thought this exam was on friday :frown:

Reply 110

rebmu

Original post by Ralphus J

Is there any chance i could have some help with Transformers, stepping up and down, i dont really get it and the equations, it would be very much appreciated.
Thanks

transformers are basically very simple you just have to use the equation vs/vp=ns/np
voltage in the secondary coil divided by the primary coil = numbers of coils in secondary coil/ number of coils in primary coil.
so its basically a ratio thing
so if you're given a question for example that if you needed to step down 230,000 volts to 230v and you had 5000 turns on the secondary coil you would simply
go 230/230,000=1/1000
1/1000= ?/5000 so the awnser is you would need 5 turns in the primary coil.
and for other things you just rearrange the formula accordingly.
and basiclaly step up tranformers have less turns in the secondary coil than the primary coil and for step down transformers as in this example the number of turns in the secondary coil is higher than the number of turns in the primary coil
think the revision guide explains it clearer than me so have a look in cgp :smile:

Reply 111

Hitdizzle

I'm in a bit of confusion here using the Left Hand Rule...
The Question i'm actually stuck on is in the A2 OCR on Page 101 question 2b).
I flew through the whole question (breaking my wrist using the LHR in the process) and got 2b) wrong.

BASICALLY, my thoughts were the direction of the Force on the Electrons would be F-D, but it's D-F.

So, I don't understand this because I thought Current was basically the flow of Electrons (i.e the flow of Current is in the same direction as Electron Drift)

Can someone please explain where I am going wrong in this stupidly easy question?

Thanks much appreciated!

Reply 112

anshul95

Original post by Hitdizzle

No the second finger for LHR and RHR represents convential current i.e. the flow of charge which in this case is opposite to the direction of the electrons (as electrons are -ve charge).

Reply 113

Summerdays

Original post by Hitdizzle

"Conventional current" is consider the flow of positive charge, which is what the left hand rule predicts (and what Ampere guessed.) But it turned out that current is the flow of negatively charged electrons. That's why you got the direction the wrong way around. Just remember that electrons flow in the opposite direction to this conventional current.

Reply 114

ChoYunEL

Original post by Hitdizzle

I'm in a bit of confusion here using the Left Hand Rule...

So, I don't understand this because I thought Current was basically the flow of Electrons (i.e the flow of Current is in the same direction as Electron Drift)
!

When using LHR or RHR, Current, your index finger points in the direction of conventional current. This is because when Fleming made the rule, he through current travels in positive charge ( + -> - ). However, we now know Electron Drift is actually the opposite ( - -> + ).
We still use Conventional current in Fleming's hand rules since it is applied to a moving positive charge.

Reply 115

ChoYunEL

Ok, here's another blast.

[INDENT]5.5.1 Structure of the universe
Candidates should be able to
(a) describe the principal contents of the universe, including stars,
galaxies and radiation;

(b) describe the solar system in terms of the Sun, planets,
planetary satellites and comets;

(c) describe the formation of a star, such as our Sun, from
interstellar dust and gas;

(d) describe the Sun’s probable evolution into a red giant and white
dwarf;

(e) describe how a star much more massive than our Sun will
evolve into a super red giant and then either a neutron star or black
hole;

(f) define distances measured in astronomical units (AU), parsecs
(pc) and light-years (ly);

(g) state the approximate magnitudes in metres, of the parsec and
light-year;

(h) state Olbers’ paradox;

(i) interpret Olbers’ paradox to explain why it suggests that the
model of an infinite, static universe is incorrect;

(j) select and use the equation ??/?= v/c;

(k) describe and interpret Hubble’s redshift observations;

(l) state and interpret Hubble’s law;

(m) convert the Hubble constant H0 from its conventional units (kms-1Mpc-1) to SI (s-1);

(n) state the cosmological principle;

(o) describe and explain the significance of the 3K microwave
background radiation.[/INDENT]

Obviously the star ones at the start have already been done but meh :colondollar:

Reply 116

Hitdizzle

Thank you very much! Big help, I understand now.
Repped! :smile:

Reply 117

Pheylan

Original post by Ralphus J

Is there any chance i could have some help with Transformers, stepping up and down, i dont really get it and the equations, it would be very much appreciated.
Thanks