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# OCR Physics B G495 Field and Particle Pictures June 21st 2011 Exam Thread watch

1. (Original post by Zagreus_92)
I have a question as well in a transformer if the current is varying sinusoidally and the question asks you to sketch a graph of flux and then emf I understand that the e.m.f is simply the differential of the flux graph but should the flux graph be in phase with the current graph or inverted or what? The mark schemes I've found are never particularly clear on this one
Flux graph is exactly the same as the current graph
2. (Original post by Soppe)
This is going to be a bad week...

Had c4 today, I should have called 999 as I basically got raped....
And then phys tomorrow, wow... How unlucky is it for some one to get raped twice in 2 days..well hopefully the phys one will be wearing a condom...

I mean it can't be any worse than c4.... I pretty much got aids/HIV from it

Bye bye university, grrr
No joke:
S3 today, Physics tomorrow, FP1 the next day, FP2 the day after that, FP3 the day after that, then as if that's not enough - Rise + Fall Retake on the Monday. FML.

Beat that
stop whining
3. (Original post by wki)
Btw . what's mean by spherical/point charge? n I'm still a bit confused of the flux density stuff~ why the curves are always sine curve and +- phi/2 phase?
A spherical charge acts like a point charge in the sense that it appears that the electric field is coming from its centre. Their electric field lines are radial.

Emf = -Ndphi/dt, phi = BA = flux

An alternating FLUX/ FLUX LINKAGE induce an emf that is also ALTERNATING. The FLUX alternates SINUSOIDALLY. The derivative of a sinusoidal wave is always a sinusoidal function that has a phase difference of 90 degrees.
4. (Original post by Soppe)
This is going to be a bad week...

Had c4 today, I should have called 999 as I basically got raped....
And then phys tomorrow, wow... How unlucky is it for some one to get raped twice in 2 days..well hopefully the phys one will be wearing a condom...

I mean it can't be any worse than c4.... I pretty much got aids/HIV from it

Bye bye university, grrr
With you on C4, messed up so bad.
5. (Original post by jimmeh)
Flux graph is exactly the same as the current graph
Correct
6. (Original post by Geekchic17)
No joke:
S3 today, Physics tomorrow, FP1 the next day, FP2 the day after that, FP3 the day after that, then as if that's not enough - Rise + Fall Retake on the Monday. FML.

Beat that
stop whining
You truly are a geek

What do you want to study?
7. (Original post by Soppe)
This is going to be a bad week...

Had c4 today, I should have called 999 as I basically got raped....
And then phys tomorrow, wow... How unlucky is it for some one to get raped twice in 2 days..well hopefully the phys one will be wearing a condom...

I mean it can't be any worse than c4.... I pretty much got aids/HIV from it

Bye bye university, grrr
Careful mate, you can't discuss C4 until midnight tonight, as Edexcel are an international exam board.
8. (Original post by Geekchic17)
No joke:
S3 today, Physics tomorrow, FP1 the next day, FP2 the day after that, FP3 the day after that, then as if that's not enough - Rise + Fall Retake on the Monday. FML.

Beat that
stop whining
Oh my. I thought A levels were finished by Friday! Unlucky, and good luck.
9. How is activity and absorbed dose related? Like what's the equation?
10. (Original post by Summerdays)
You truly are a geek

What do you want to study?
Ahaha, Mechanical Engineering hopefully (providing i don't get 'raped' by physics lol)
11. (Original post by jimmeh)
Flux graph is exactly the same as the current graph
The mark scheme said in or out of phase as well, so I assume that means completely in or out of phase or in other words shifted?
12. (Original post by Geekchic17)
No joke:
S3 today, Physics tomorrow, FP1 the next day, FP2 the day after that, FP3 the day after that, then as if that's not enough - Rise + Fall Retake on the Monday. FML.

Beat that
stop whining
Who's there !
S !
S who ?
SOS !
Getting a bit bored of revision though I still got loads to do .. yeah who needs sleep LOL Good luck mates x
13. (Original post by jimmeh)
Oh my. I thought A levels were finished by Friday! Unlucky, and good luck.
Yeah sucks to be me eh.
14. (Original post by jimmeh)
Oh my. I thought A levels were finished by Friday! Unlucky, and good luck.
Are you not taking G494 then? Thought everyone does both units in the summer.
15. (Original post by Summerdays)
A spherical charge acts like a point charge in the sense that it appears that the electric field is coming from its centre. They're electric field ines are radial.

Emf = -Ndphi/dt, phi = BA = flux

An alternating FLUX/ FLUX LINKAGE induce an emf that is also ALTERNATING. The FLUX alternates SINUSOIDALLY. The derivative of a sinusoidal wave is always a sinusoidal function that has a phase difference of 90 degrees.
does it mean that if it alternating current a.c , then the flux linkage is alternating?
what if it's dc then? Have I messed them all up?
16. (Original post by Geekchic17)
Ahaha, Mechanical Engineering hopefully (providing i don't get 'raped' by physics lol)
AWESOME. Which Uni?
17. (Original post by Zagreus_92)
I have a question as well in a transformer if the current is varying sinusoidally and the question asks you to sketch a graph of flux and then emf I understand that the e.m.f is simply the differential of the flux graph but should the flux graph be in phase with the current graph or inverted or what? The mark schemes I've found are never particularly clear on this one
I don't think they are particularly bothered about whether it's inverted or not. Our physics teacher said that it isn't specified in the syllabus.

I haven't come across any markschemes which don't allow both, all they seem to give marks for is being 90 degrees out of phase.
18. (Original post by Zagreus_92)
The mark scheme said in or out of phase as well, so I assume that means completely in or out of phase or in other words shifted?
Yeah, doesn't matter. I always go for in phase, just in case my brain has a mini-stroke or something and I get it wrong...

(Original post by Swindan)
Are you not taking G494 then? Thought everyone does both units in the summer.
Nope, everyone at college does it in January. Definitely lessens the load in the summer. I didn't know it was that late though! Sucks to be all of you! (I kid, I kid...Good luck, will be worth the effort eventually)
19. (Original post by wki)
does it mean that if it alternating current a.c , then the flux linkage is alternating?
what if it's dc then? Have I messed them all up?
Yes for the first part.
D.C is direct current... which isn't alternating. A commutator, if you're referring to a motor, is used though.
20. (Original post by Summerdays)
AWESOME. Which Uni?
Er Southampton/Sheffield
Sheffield more likely cause it's lower grades haha
What are you wanting to do? and where?

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