OCR Physics A G485 - Frontiers of Physics - 18th June 2015

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Reply 1040

Elcor

For June 2011 question 2, why is the induced e.m.f. in the secondary coil not alternating?

Reply 1041

Makashima

Original post by jcwh97

There is nothing stopping them from repeating questions. It has happened before.

suppose so
but if so then i dont mind, i remember the ms anyway

Reply 1042

actanide

Original post by Elcor

For June 2011 question 2, why is the induced e.m.f. in the secondary coil not alternating?

i think you dont mean question 2 June 2011 because theres nothing to do with EMF in there hehe

Reply 1043

I Persia I

Guys is the mass defect the release of energy when fission occurs ie the 'explosive' energy released in a nuclear bomb? Also how is energy released in fusion and why is it greater than in fission?

Reply 1044

actanide

mass defect is just the change of the mass between before of the reaction and after the reaction. Theres usually more mass before the reaction and then less mass after because the energy is released

Fusion releases more energy because the mass defect is bigger.
Fusion releases energy in the form of photons and KE

Reply 1045

Doctopus

Guys, what topics do we think are mostly to come up?

Reply 1046

I Persia I

Original post by actanide

And the release in energy can be found by mass defect x c^2 right?

Reply 1047

actanide

Original post by I Persia I

And the release in energy can be found by mass defect x c^2 right?

mhm

Reply 1048

ETRC

Original post by xy0mz

Could someone pls explain 9.(c) in June14, preferably with a diagram? Cheers. ImageUploadedByStudent Room1434540632.795327.jpg

Posted from TSR Mobile

is it 0.379?

Reply 1049

Elcor

Original post by actanide

i think you dont mean question 2 June 2011 because theres nothing to do with EMF in there hehe

Q1 actually

Posted from TSR Mobile

Reply 1050

chem@uni

Original post by Doctopus

Guys, what topics do we think are mostly to come up?

The ones in the spec

Reply 1051

actanide

Original post by chem@uni

The ones in the spec

yeah its kind of a stupid question, this is physics, this is not Sociology where you have a set of questions that they can ask you.

Just learn everything, and hope for the best.

Reply 1052

chem@uni

Original post by actanide

yeah its kind of a stupid question, this is physics, this is not Sociology where you have a set of questions that they can ask you.

Just learn everything, and hope for the best.

Yeah I agree you cant really predict what will come up I mean if something came up very heavily the year before you can maybe revise that a little less but that isnt really guaranteed

Reply 1053

Mr_Cupcakes

Original post by actanide

yeah its kind of a stupid question, this is physics, this is not Sociology where you have a set of questions that they can ask you.

Just learn everything, and hope for the best.

I'd disagree, they're trying out new stuff. We're this far into the spec now with some things still yet to come up- mass spectrometers? B-scans and PET scans came up last year, will they come again this year? Probably not.

Reply 1054

ETRC

pls gamma camera, evolution of universe from big bang or evolution of sun, PET, speed of blood, smoke alarms or age of relics come up

nice 25 marks right there

Reply 1055

chem@uni

Original post by ETRC

pls gamma camera, evolution of universe from big bang or evolution of sun, PET, speed of blood, smoke alarms or age of relics come up

nice 25 marks right there

WRite answer for each of them haha

Reply 1056

coder4

Original post by actanide

someone halp pls

I hate that question

Reply 1057

ETRC

Original post by chem@uni

WRite answer for each of them haha

Gamma Camera
COLLIMATOR- gamma ray photons travel along lead tubes
SCINTILLATOR- gamma ray photon converted to many photons of visible light
PHOTOMULTIPLIER TUBES- photon of visible light produces electrons
COMPUTER- generates image

Big Bang
-singularity and infinitely hot at start
-all forces are unified
-rapid expansion led to cooling and a soup of quarks and leptons formed
-more matter than antimatter
-when cool enough the quarks combined to form protons and neutrons and primordial helium forms
-more protons than neutrons (4:1 ratio)
-gravitational forces responsible for formation of stars and galaxies
-modern day 2.7K background radiation originally gamma radiation

Smoke Detector
-Americium-241 used as an alpha particle source
-a particles ionise air particles in chamber so current flows in circuit
-when smoke particles enter detector, the a particles ionise smoke particles instead of air particles so the current decreases
-at a certain threshold the current is too low and circuit breaks and alarm goes off

PET
-positron emitting substance injected into body
-electron and positron annihilate each other producing two gamma ray photons travelling in opposite directions
-ring of gamma detectors surrounds patient
-3-d image created using detectors and a computer
-arrival time of photons used to locate areas of increased activity

Carbon dating
-organisms absorb c-14 when alive
-stop taking in c-14 when dead
-ratio of c-14 to c-12 calculated for dead sample and a modern day sample
-x=xe-yt and ratio used to determine age of organism
-ratio of c-12 to c-14 assumed to be constant

cba anymore

Reply 1058

rw99

on the june 2011 paper Q5a how are you supposed to work out the force is downwards? Obviously you use the left hand rule but i can't find where in the question it gives you the information you need. You're given the direction of the current but it just says the magnetic field is perpendicular to it, it doesn't give you its direction. I guessed and went with upwards but it's downwards. Any ideas?