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# G485 June 2012 Paper and unofficial mark scheme

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1. Hi all
I've scanned a copy of the paper and I plan to write up an unofficial mark scheme.

The file is too large to attach.
Here is a link to paper via my skydrive.
https://skydrive.live.com/redir?resi...D4F043877A!196
(It can be slow to load, just be patient)
2. Unofficial mark scheme
Please free feel to offer your opinions, I by no means claim to know all the answers, far form it.

With thanks to:
jamesvernon
Hamer

(Working Progress)

Question 1:
(a) A capacitor has a capacitance of one farad when it can store a charge of one coloumb per unit potential difference/volt

(b) (i) 1/Capacitance? (i) Energy stored by the capacitance

(c) 58.8 microF + a nice picture of them all in series

(d) (i) QIt, Q=2.4 (ii) Q=vc v=Q/c = 24 W=1/2 x Qv = 28.8J

Question 2:
(a)
(i) Arrow to centre of Circle
(ii) The force always acts perpendicular to motion hence there is no component of the force effecting the motion

(b) 1.37x10^-14 J

(c) 1.42x10^-3 T

(d) 2.4x10^-12 m + Resoning that assume both positron + electron are both converted to pure energy

Question 3:
(a)(i) Frequency = 1/Period
Frequency = 1/10x^-3
Frequency = 100 Hz

(ii) Magnetic flux linkage = B A N
B = Magnetic flux linkage / A N
B = 2x10^-2/1.6x10^-3 x 400
B = 0.03125 (0.0313 to 3 s.f.)

(iii) For this question you needed to make a gradient triangle between 2 seconds and 3 seconds. The magnetic flux density changes from 0.6x10^-2 to -0.6x10^-2 in 1x10^-3 seconds:

Emf = Change in magnetic flux density / Change in time
Emf = 1.2x10^-2/1x10^-3
Emf = 12V

(b) P = V^2/R
P = 12^2/150
P = 0.96W

Question 4:
(a) Conservation of momentum, initial momentum of alpha is equal to the final momentum of gold nucleus. The force that slows down alpha particle accelerates gold nucleus to left.
(b) Lines curing towards from points
(c) F = Q1Q2/(4 pi eo r^2) = (79 x 1.6E-19 x 2 x 1.6E-19) / (4 pi eo x 6.0E-14^2) = 10.1N
(d) 1/R^2 graph

Question 5:
(a) No of neutrons = 234-92 = 142
(b) (i) KE= 5.6MeV = 5.6 x 1E6 x 1.6E-19 = 8,96E-13J (ii) KE = 1/2 mv^2 so v = sqrt(2 x 8.96E-13 / 6.65E-27) = 1.64E7 ms-1
(c) (i) Power = Activity x energy of 1 event, A = 62/8.96E-13 = 6.92E13 Bq (ii) n2 / t1/2 = 0.693/(88 x 3.16E7) = 2.49E-10 s-1
(ii)

Question 6:
(a)
(b)
(c) (i) (ii) (iii)
(d)

Question 7:
(a) ONE from; A type of EM Radiation, Can travel in a vacuum, Short waves lengths (x10-8...x10-12), High energy, Ionising, Travel Transversely

(b) Compton Effect is the process by which a x-ray loses some of its energy when it is incident on an electron in an atom, ejecting the electron and leaving the nucleus so that momentum is conserved.

(c) (i) Initial Intensity of the Collimated Beam (ii) 0.21 CM

(d) To Show up an organ more clearly, because it is almost indistinguishable from similar soft tissue around it.

Question 8:
(a) Most nuclei behave as small magnets with a north and south pole.
When a strong magnetic field is applied, the nuclei align their magnetic axes parallel to the external magnetic field.
They show precession and the angular frequency of precession is known as the Larmor frequency.

(b) A PET scan in loves ionising radiation as gamma-ray photons are produced. An MRI does not involve ionising radiation. For a PET scan, the patient must be injected with a radioactive source. This is not necessary for an MRI scan.

Question 9:
(a) Light nuclei can become more stable by joining together in via a fusion reaction.
Fusion reactions take place at extremely high temperatures, above 10^7K. The atoms also need a large amount of kinetic energy.

(b) Explodes as a supernova, for a star of 3-10 solar masses the remnant core is a neutron star. For a stare greater than 10 solar masses, the core undergoes further collapse, resulting in a black hole.

Question 10:
(a) F= GMm/r^2 6.67x10^-11 x (1.0x10^11 = 1.0 x10^30)^2/(4.0x10^22)^2

(b) The gravitational force between them is not strong enough to cause them to collapse/fall into each other.

(c) Big bang. All matter and energy is concentrated in a single point in space.
All four forces are unified (gravitational, electrostatic, strong nuclear and weak nuclear) Expansions occurring rapidly.
Gravitational force becomes prominent. Photons and quarks appear.
Strong nuclear force becomes prominent. Quarks form leptons. Already more matter than antimatter present.
Weak nuclear force and electrostatic force become prominent. Increasing amounts of matter. Antimatter disappear (from our galaxy)
Helium and Lithium form. Matter is in the form of plasma.
Atoms form. Photons travel freely. Cosmic background radiation forms.
Density fluctuations result in the first structure if the universe.
Further structure form. Heavy element form.

Obviously not all this is needed, just 5/6 statements in correct order.
(d)
(i) The spectrum contains dark lines called absorption spectral lines. These represent photons that have been absorbed by the sample.
(ii) Doppler equation, rearrange to find the speed

v= Hubbles constant x d
d= v/Hubbles constant
3. So what, you're "reserving" the thread?
4. (Original post by Picture~Perfect)
Hi all
I've scanned a copy of the paper and I plan to write up an unofficial mark scheme.

The file is too large to attach.
Here is a link to paper via my skydrive.
https://skydrive.live.com/redir?resi...D4F043877A!196
(It can be slow to load, just be patient)
Sweet, thanks
5. hurry up, how long does it take you to write a mark scheme, jeezzzz
it only took me 2h to write the exam
6. (Original post by tallen90)
So what, you're "reserving" the thread?
No, I'm done, I just needed the first two posts. One for the paper and one for the mark scheme.
7. (Original post by zabuzar)
hurry up, how long does it take you to write a mark scheme, jeezzzz
it only took me 2h to write the exam

How rude. Picture~Perfect is being kind enough to write it out for all of us. The least you can be is thankful. She can take as much time as she needs. I don't see you writing one up?
8. (Original post by Picture~Perfect)
No, I'm done, I just needed the first two posts. One for the paper and one for the mark scheme.
Oh, okay, fair enough well done on getting it uploaded so quickly!
9. (Original post by SS*)
How rude. Picture~Perfect is being kind enough to write it out for all of us. The least you can be is thankful. She can take as much time as she needs. I don't see you writing one up?
someone needs sarcasm lessons
I was also pointing out the fact that it took me the whole 2h to finish the exam, which suggest that i found it really hard.

P.S.
thanks for the mark scheme PP
10. (Original post by zabuzar)
hurry up, how long does it take you to write a mark scheme, jeezzzz
it only took me 2h to write the exam
My friend, with that attitude you will fail both the exam and life
Good day to you
11. I'll do some later one's cause you're probably starting at the start :P

Question 7:
(a) TWO from; A type of EM Radiation, Can travel in a vacuum, Short waves lengths (x10-8...x10-12), High energy, Ionising, Travel Transversely

(b) Compton Effect is the process by which a x-ray loses some of its energy when it is incident on an electron in an atom, ejecting the electron and leaving the nucleus so that momentum is conserved.

(c) (i) Initial Intensity of the Collimated Beam
(ii) 0.21 CM

(d) To Show up an organ more clearly, because it is almost indistinguishable from similar soft tissue around it.
12. (Original post by jamesvernon)
I'll do some later one's cause you're probably starting at the start :P

Question 7:
(a) ONE from; A type of EM Radiation, Can travel in a vacuum, Short waves lengths (x10-8...x10-12), High energy, Ionising, Travel Transversely

(b) Compton Effect is the process by which a x-ray loses some of its energy when it is incident on an electron in an atom, ejecting the electron and leaving the nucleus so that momentum is conserved.

(c) (i) Initial Intensity of the Collimated Beam
(ii) 0.21 CM

(d) To Show up an organ more clearly, because it is almost indistinguishable from similar soft tissue around it.
I was actually working backwards, which is what I did in the exam, but I appreciate any help, thank you
13. For the distance in MPc one I did:

(480-393.4)/480 = v/3x10^8

Got v ~ 5x10^7ms^-1

Then divide by 50 to get about 1200. Can't remember the exact values though
14. (Original post by mack94)
My friend, with that attitude you will fail both the exam and life
Good day to you
oh no
someone on the internet said I'm going to fail in life, and in my exams

i should kill myself now rite?
15. (Original post by joefoxon)
Can't remember the exact values though
i got 1320Mpc
there was a decimal point and a digit after but i rounded to 3s.f.
16. Question 1:
(a) A capacitor has a capacitance of one farad when it can store a charge of one coloumb per unit potential difference/volt

(b) (i) 1/Capacitance
(ii) Energy stored by the capacitance

(c) 58.8 MewF + a nice picture of them all in series

(d)(i) q=it, q=2.4
(ii) 0.96 W
17. (Original post by zabuzar)
i got 1320Mpc
there was a decimal point and a digit after but i rounded to 3s.f.
Actually, I got 1082.5 , I just put it into my calculator. I imagine they'll accept both values though, if you divide by 480 or 39whatever :P
18. (Original post by jamesvernon)
Question 1:
(a) A capacitor has a capacitance of one farad when it can store a charge of one coloumb per unit potential difference/volt

(b) (i) 1/Capacitance
(ii) Energy stored by the capacitance

(c) 58.8 MewF + a nice picture of them all in series

(d)(i) q=it, q=2.4
(ii) 0.96 W
0.96W?
Its asking for the energy stored in joules.
Q=vc v=Q/c = 24 W=1/2 x Qv = 28.8J
19. Question 2:
(a)(i) Arrow to centre of Circle
(ii) The force always acts perpendicular to motion hence there is no component of the force effecting the motion

(b) 1.37x10^-14 J

(c) 1.42x10^-3 T

(d) 2.4x10^-12 m + Resoning that assume both positron + electron are both converted to pure energy
20. I'll be back later to finish this off.

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