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# AQA Physics PHYA4 - Thursday 11th June 2015 [Exam Discussion Thread] watch

1. Why is the answer B and not A? Where does the x^2 come from?
2. (Original post by 000alex)
Does the t in the third equation mean time after the rotation has started?
Yes, if you think about it, the function in the third equation gives you the angle the coil has turned through relative to the initial point.

Taking the sine of this angle gives you the component of the peak EMF induced when the coil rotates at an angle theta to the normal of the coil face.

Hope that helps!

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Why is the answer B and not A? Where does the x^2 come from?
http://www.thestudentroom.co.uk/show...9#post56360579

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4. Thank you!
Thank you!
No worries! Hope that clears it up.

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6. (Original post by CD223)
No worries! Hope that clears it up.

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Yes this method is a lot easier than the one I used unsuccessfully aha.
I guess you're confident for this exam?
7. Does anybody have the answer to these, are teacher gave us this document to help us with some a2 but don;t know where its from. Thanks in advance
Attached Images
8. SYNOPTIC-LOOKS INTERESTING.pdf (363.0 KB, 299 views)
Yes this method is a lot easier than the one I used unsuccessfully aha.
I guess you're confident for this exam?
Not confident at all! I like physics but I don't like exams and the papers this year are so easy to slip up on! You?

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10. (Original post by Sonnyjimisgod)
Does anybody have the answer to these, are teacher gave us this document to help us with some a2 but don;t know where its from. Thanks in advance
Haven't personally seen them, sorry. Curious as to why it's unit 6 though? Shouldn't it be unit 4?

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11. help with this one please
12. (Original post by Sonnyjimisgod)
Does anybody have the answer to these, are teacher gave us this document to help us with some a2 but don;t know where its from. Thanks in advance

http://studentbounty.com/pastpapers/...0&%20Specimen/

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13. (Original post by AR_95)

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14. How do u know the distance is square root 2a, I thought it was just 2a

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The only thing I have trouble with on unit 4 is knowing which hand to use with Generators, motors, emf etc.....

For some reason it is extremely confusing to me. I understand how to use the actual hand itself but, I can't figure out when I have to use it!

Help would be much appreciated!
16. (Original post by huniibehi)
How do u know the distance is square root 2a, I thought it was just 2a

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By Pythagoras, with the side length of 2a, each of the diagonals has a length of .

As P is at the centre of the square (and the centre of each diagonal), the distance to each charge is

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17. (Original post by CD223)
By Pythagoras, with the side length of 2a, each of the diagonals has a length of .

As P is at the centre of the square (and the centre of each diagonal), the distance to each charge is

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Oh I see, thanks! The struggles of doing a level physics without a level maths!

The only thing I have trouble with on unit 4 is knowing which hand to use with Generators, motors, emf etc.....

For some reason it is extremely confusing to me. I understand how to use the actual hand itself but, I can't figure out when I have to use it!

Help would be much appreciated!
Motors/charges moving in magnetic fields = left hand rule

Generators/generating or inducing an emf = right hand rule

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19. (Original post by huniibehi)
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Oh I see, thanks! The struggles of doing a level physics without a level maths!
Haha, no worries

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20. (Original post by CD223)
Motors/charges moving in magnetic fields = left hand rule

Generators/generating or inducing an emf = right hand rule

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Thank you so much mate! Seems simple but, it just confused me so much like!
Thank you so much mate! Seems simple but, it just confused me so much like!
No worries! I guess just always use the left hand rule, except when Generating an EMF, where the Right hand rule is used

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