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# AQA Physics PHYA4 - 20th June 2016 [Exam Discussion Thread] watch

1. Is the electric field always the negative of the potential gradient?
2. How many repeated questions will there be in the MC?

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3. What does it mean about the radial to non radial thing? Does someone mind drawing exactly what is required? thanks
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4. Anyone got any tips for being fast (ish) on the multiple choice? I just did one and only answered 12.....
5. (Original post by Nikhilm)
What does it mean about the radial to non radial thing? Does someone mind drawing exactly what is required? thanks
Hmm, they are both positive point charges. Imagine when there electric fields meets, what's going to happen to the lines? Their radial pattern will change.
6. (Original post by Throor)
Anyone got any tips for being fast (ish) on the multiple choice? I just did one and only answered 12.....
Keep doing past papers, it honestly really helps with the timing.
7. (Original post by particlestudent)
Hmm, they are both positive point charges. Imagine when there electric fields meets, what's going to happen to the lines? Their radial pattern will change.
It wouldn't change to non radial though? I think they're talking about the back end of the charges but I'm not 100%, hence requesting someone to draw a diagram
8. (Original post by Nikhilm)
It wouldn't change to non radial though? I think they're talking about the back end of the charges but I'm not 100%, hence requesting someone to draw a diagram
Take a look at this diagram to give yourself an idea of what they mean. Modify that diagram to suit the magnitude of the charges they used.
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9. (Original post by particlestudent)
Take a look at this diagram to give yourself an idea of what they mean. Modify that diagram to suit the magnitude of the charges they used.
Ah thanks!
10. (Original post by Nikhilm)
Ah thanks!
No problem .
11. Can somebody explain to me why this one is C?
12. (Original post by CD1998)
Can somebody explain to me why this one is C?
It is moving parallel to the field so it won't experience a force.

No force means no acceleration so no change in speed.
13. Can someone please help me? Q24 june 13 section A. I get the emf bit but not the direction. Thanks
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14. (Original post by particlestudent)
Yes, a negative charge moving to the right for example has to be treated as a positive charge moving to the left.

Electric field lines show you the direction a positive charge would move if it was placed in that field.
thank youuu
15. Multiple Choice section seems ok now after 5 past papers

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16. (Original post by Yo12345)
Multiple Choice section seems ok now after 5 past papers

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Which papers have you done?
17. (Original post by particlestudent)
Which papers have you done?
Jan 2010 - Jan 2012 at home. Just need to do June 12 and Jan 13 tomorrow and June 2013 on Sunday. June 2014 and 15 as mocks. What about you?

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18. http://prntscr.com/bhq9df

I'm failing to see why the answer isn't D. If the magnet is decelerating once it enters the coil (due to Lenz's law) surely this means that the lines of flux cut per second decreases from a given value to zero.

Edit: nvm I think I got it. I might have been getting confused with rate of change of flux linkage and simply flux linkage, i.e. the explanation is that the flux linkage rises from 0 to a value as it enters the field, creating a rate of change and thus inducing emf (causing a current reading to be displayed), but then that change stops occurring, so there's no more induced emf
19. (Original post by ¡Muy bien!)
Can someone please help me? Q24 june 13 section A. I get the emf bit but not the direction. Thanks
Magnetic flux=BA
Area which the rod moves through= length * distance covered
(where distance covered, d, equals velocity * time taken, from v=s/t)
Magnetic flux equals BLvt, emf induced equals the rate of change of flux density.
Therefore EMF=BLvt/t, the t's cancel, so the emf=BLv.
20. (Original post by Yo12345)
Jan 2010 - Jan 2012 at home. Just need to do June 12 and Jan 13 tomorrow and June 2013 on Sunday. June 2014 and 15 as mocks. What about you?

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Well I've done all of them and gone over them again. I found (for Section A) Jan11,Jan13,Jun14 and Jun15 tricky.

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