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

1. (Original post by KD1997)
yeah i didn't know what to do for the mcq, so i went for the longest one A but i'm pretty sure i got it wrong.

for the limiting facrto though i wrote what you did but I'm sad to say we're both wrong. The limitation is that the formula is only accurate for angles of displacement of 10 degrees or less since the dervivation of the formula uses the small angle approximation to say gsin theta=g
I did say 10 degrees though. And I'd just assume the examiners will understand why I didn't explicitly say 'or less than' as there's no way it would go higher than the angle.
2. For the last question on section B, I thought that no current is induced in the wheel because it's not connected to a circuit? So there's a magnetic force on the wheel which causes it to slow down but no current. Does anyone know if i'm going to lose marks if I didn't talk about electromagnetic induction in that part?
3. (Original post by Yo12345)
Do you remember any others. Transformer one with the table was B? The one with the left hand rule was 0.0075N upwards

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Yes I got these, the transformer was repeat from another year wasn't it
I can't remember off top of my head but if you ask I might remember. I got C^2kg^-1 as the EG one is all I remember lol
(Original post by particlestudent)
If I thought N was the original mass of nucleus and got mv/(N-m) for V and attempted to find the Ea formula, would I get 0 marks on both of them? I hope I get some on the Ea one...
You might get a mark but I couldn't tell, because this was a new question
4. (Original post by particlestudent)
It's a scalar so it's the sum, 1+(-4)
But that wouldn't work in the case of the square one, it had to be minus?

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5. (Original post by Yo12345)
But that wouldn't work in the case of the square one, it had to be minus?

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The square one was zero, that was the electric field strength if I remember correctly.
6. (Original post by particlestudent)
The square one was zero, that was the electric field strength if I remember correctly.
You're right, my mistake

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7. (Original post by BlueSi)
For the last question on section B, I thought that no current is induced in the wheel because it's not connected to a circuit? So there's a magnetic force on the wheel which causes it to slow down but no current. Does anyone know if i'm going to lose marks if I didn't talk about electromagnetic induction in that part?
I said current/emf is induced that opposes the change in blah blah blah
8. (Original post by Yo12345)
EoG = no unit

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If you equal force due to electric and force due to gravity and rearrange you end up with E0 * G being Q^2/m^2 so it was C^2 kg^-2.
9. (Original post by TheLazyGuy1)
transformer one in table was D

d,b,b,d,d,c,d,b,b,c,b,c,c,a,c,a, d,a,c,a,a,d,c,a,d
10. What would 54 to 58 marks be?
11. (Original post by Mentalmirz)
The pendulum one was B because it was the same length therefore the frequency was the same so undergoes resonance.

The charge moving along the field line wasn't constant, It was either increasing or decreasing but I can't remember which.

the capacitance one is definitely correct and I can't remember the others
Charge was moving along a field line so potential must have been constant?

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12. (Original post by C0balt)
Yes I got these, the transformer was repeat from another year wasn't it
I can't remember off top of my head but if you ask I might remember. I got C^2kg^-1 as the EG one is all I remember lol

You might get a mark but I couldn't tell, because this was a new question
Do you remember what you got for the very last transformer question, about why high voltages are needed? It's definitely so that current is lower, right?
13. (Original post by Yo12345)
Charge was moving along a field line so potential must have been constant?

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A field line and equipotential isn't the same. The charge was moving away from the point charge I think
14. (Original post by tanyapotter)
Do you remember what you got for the very last transformer question, about why high voltages are needed? It's definitely so that current is lower, right?
Yeah
15. (Original post by tanyapotter)
Do you remember what you got for the very last transformer question, about why high voltages are needed? It's definitely so that current is lower, right?
I ticked the one about current is lower for the same effective power or something like that
16. (Original post by particlestudent)
What would 54 to 58 marks be?
this is probs what I got or lower I'm hoping for 50-58 tbh. I have no idea why this would be !? anyone ??
17. (Original post by Jordenwilder1998)
what did everyone put for the box tick question. i cant remember exactly what it was but could someone clarify
i remember they asked for when the rate of change of charge lowest

the answer was between the last two options.
about the pd across the resistor or the current through it
18. Do people remember which way the coil is turned for max/min flux?

I put the very bottom box: pi/3 anticlockwise and pi/6 clockwise?
19. (Original post by C0balt)
Yeah
For the transformer question I may have picked the one with both >1 silly me
20. (Original post by tanyapotter)
Do you remember what you got for the very last transformer question, about why high voltages are needed? It's definitely so that current is lower, right?
No, why would you want current to be lower? That increases power loss due to resistance. I put because industry often needs high voltages (B I think?).

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