AQA Physics Unit 1 PHYA1 20th May 2013

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I love the quantum phenomena topic for this unit, but I have never been able to get my head around Feynman diagrams or interaction :frown:

and I just find electricity a real chore to revise. Which sucks cause I really need an A by the end of this year :frown:

Reply 501

x-Sophie-x

Original post by Felix Felicis

Ok, so you can work out the total resistance to be

R_{T} = \left( \dfrac{1}{40 \times 10^{3}} + \dfrac{1}{15 \times 10^{3}} \right)^{-1} = \dfrac{120 \times 10^{3}}{11} \ \Omega \Rightarrow I = \dfrac{V}{R} = 1.1 \times 10^{-3} A

Now, when the voltage branches off into the 2 parallel branches, the voltage stays the same (each coulomb of charge still has the same amount of energy) but the current splits as the charges split. Call the current across A-E

I_{1}

and the current across B-F

I_{2}

From conservation of energy, you know that the potential difference (i.e. the voltage drop) across A-E has to be 12V as when the current branches from E and goes back to the cell, there should be a drop of 12J in every coulomb of charge, therefore you know that by Ohm's law

12 = I_{1} \times (20 \times 10^{3} + 20 \times 10^{3} ) \Rightarrow I_{1} = \dfrac{12}{40 \times 10^{3}} = 3 \times 10^{-4} A

Thus, the potential difference across A-C is

3 \times 10^{-4} \times 20 \times 10^{3} = 6V

By similar arguments, you can calculate the potential difference across BD and the difference in C-D is just the difference in potential difference from AC and BD.

You again! :P

Are you even doing this exam? haha

But thank you- that was a really useful explanation :h:

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Reply 502

Big-Daddy

Any advice for the electricity diagram questions?

Is it just: a) be able to draw potential divider circuits; b) be able to draw variable resistor circuits; c) always have an ammeter in series, and a voltmeter in parallel, with whatever you're measuring. Anything else?

Reply 503

danlocke

Can someone give a simple explanation of why there is a maximum value for E_k in the photoelectric effect?

Thanks

Reply 504

Substitution

Original post by Alistair_Mallard

Anyone got any bets on what the long answer question will be on?

last year: oscilloscope
year before: circuit
year before: circuit
year before: circuit
year before: photoelectric
year before: photoelectric
year before: photoelectric

it is screaming out to be another oscilloscope to me

Reply 505

Big-Daddy

What sort of things are on every 6-mark experiment question's mark scheme? Such as taking repeat readings, etc.

Reply 506

Felix Felicis

Original post by x-Sophie-x

You again! :P

Are you even doing this exam? haha

But thank you- that was a really useful explanation :h:

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Me again... :wink:

Lolno, OCR ftw. xD But I'm bored from my chem/ geog revision and decided to go on TSR considering I'm gated. xD I see physics question, I do random physics question => Monkey see, monkey do....xD

No probs :wink:

Reply 507

StalkeR47

Original post by danlocke

Can someone give a simple explanation of why there is a maximum value for E_k in the photoelectric effect?

Thanks

Photons have energy dependent on frequency. Each electron absorbs the energy from 1 photon and therefore gains energy = hf, where hf is the energy of a light photon. An electron can leave the metal surface if the energy gained from a single photon exceeds the work function of the metal. therefore, the maximum ke of emitted electron is given by ek=hf-work function. (The intensity does not effect the max ke of a photoelectron). No matter how intense the light is, the electron will still absorb 1 photon, and there gains max kinetic equal to hf-work function.

(edited 10 years ago)

Reply 508

Alistair_Mallard

Original post by BenChard

Internal resistance experiment though? never come up, and surely thats a contender?

Reply 509

Goods

Original post by BenChard

They won't ask exactly the same question and theres no other reasonable questions to ask about osciloscopes

Reply 510

x-Sophie-x

Original post by Goods

They won't ask exactly the same question and theres no other reasonable questions to ask about osciloscopes

I think the same.
And I seriously hope it isn't oscilloscopes..I hate them.

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Reply 511

vengeance111

anyone got a link to the jan 13 paper ?
preferably mark scheme to

Reply 512

charliedoubleyou

Original post by BenChard

if it is another oscilloscope question i will cry into my hands

Reply 513

StalkeR47

Original post by vengeance111

anyone got a link to the jan 13 paper ?
preferably mark scheme to

http://www.thestudentroom.co.uk/showthread.php?t=2317448&page=22&page=22 end post

Reply 514

Substitution

Original post by Alistair_Mallard

Internal resistance experiment though? never come up, and surely thats a contender?

earlier in the thread I did suggest it could be a question on emf and internal resistance, just internal resistance would be too easy simply connect an ohmmeter to the battery

Original post by Goods

They won't ask exactly the same question and theres no other reasonable questions to ask about osciloscopes

fair point I know my oscilloscopes inside out just In case. most likely is emf and internal resistance from a graph or possibly work function and threshold frequency from a graph.

Reply 515

Bixel

Original post by BenChard

Could possibly well be an oscilloscope :P

Reply 516

Qari

Original post by StalkeR47

http://www.thestudentroom.co.uk/showthread.php?t=2317448&page=22&page=22 end post

Doing this paper and it's asked for energy but it's got answer in Watts, is that a mistake because I thought energy is in Joules

http://filestore.aqa.org.uk/subjects/AQA-PHYA1-W-QP-JUN11.PDF Question 6 d)ii