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Original post by saad97
Have you done magnetic fields and do you have any decent notes on it? My teacher rushed through it pretty much so I'm all confused about the whole section. -.-
But yeah I think we've finished it all. (AQA as well.)


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yeah we've done magnetic fields, but I don't really have any good notes. soz bro
Reply 21
Does anyone have the June 2014 papers for Unit 4 or 5 please?


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Original post by Inevitable
Does anybody by any chance have the OCR A Physics G481: Mechanics paper (or mark scheme) from May 2014? If so, could you please upload it.

Much appreciated.


This paper will not be publicly available until summer 2015 (apart from to schools who are likely to use it for mock exams).

I have recorded video walkthroughs for the June 2013 OCR Mechanics paper, if that's any help? Follow the links in my profile/signature for other revision videos.

[video]https://www.youtube.com/playlist?list=PLBb_6jpE41oIWJQGu 9kolpxHTYsxT5svH[/video]
Any edexcellers? :biggrin:
Does anyone have a definition for the unit of magnetic flux, the Weber? I can't find it in either of my textbooks and I have an exam next week. Since we got a new teacher, we haven't been getting any notes. I literally have two half pages of notes on Magnetic Fields, and one of them is a table from an experiment.-.- I'm CCEA, but tbh at this point I'll be thrilled to have the definition from any exam board out there. Help would be much appreciated :smile:
Original post by crozibear96
Does anyone have a definition for the unit of magnetic flux, the Weber? I can't find it in either of my textbooks and I have an exam next week. Since we got a new teacher, we haven't been getting any notes. I literally have two half pages of notes on Magnetic Fields, and one of them is a table from an experiment.-.- I'm CCEA, but tbh at this point I'll be thrilled to have the definition from any exam board out there. Help would be much appreciated :smile:


Been a while since I've done it, but according to the OCR A official textbook, 1 Wb = 1 T m2.

This is because magnetic flux is the product of the magnetic flux density B (measured in T) and the area when the field is at right angles to the area. This gives Φ = BAcosθ. So because B is in Tesla and A is in square metres (and cosθ is a function of the angle, so it has no units), you get T x m2.
Original post by crozibear96
Does anyone have a definition for the unit of magnetic flux, the Weber? I can't find it in either of my textbooks and I have an exam next week. Since we got a new teacher, we haven't been getting any notes. I literally have two half pages of notes on Magnetic Fields, and one of them is a table from an experiment.-.- I'm CCEA, but tbh at this point I'll be thrilled to have the definition from any exam board out there. Help would be much appreciated :smile:


I Weber is the magnetic flux which induces in a coil of 1 turn an emf of one volt when it is reduced to zero in one second.

The definition is based on Faraday's Law.
Original post by Crydamoure


Original post by Stonebridge


Thank you both so much.:smile:
Hey, I'm doing AQA A2 Physics, and have been revising for my mocks (Physics is on the 12th I think). Up till now, I've been doing mainly stuff out of my revision book, and it's been going really well. Today I switched over to doing past papers, and suddenly everything has gotten a heck of a lot harder, specifically with the multiple choice stuff (I'm doing Spec A).
What would you guys advise me to do to get better at the multiple choice stuff? Any shortcuts, or tips? And not just more practice, cos I'm going to be doing a lot of that.
Thanks for your advice.
Reply 29
Original post by l1lvink
Hey, I'm doing AQA A2 Physics, and have been revising for my mocks (Physics is on the 12th I think). Up till now, I've been doing mainly stuff out of my revision book, and it's been going really well. Today I switched over to doing past papers, and suddenly everything has gotten a heck of a lot harder, specifically with the multiple choice stuff (I'm doing Spec A).
What would you guys advise me to do to get better at the multiple choice stuff? Any shortcuts, or tips? And not just more practice, cos I'm going to be doing a lot of that.
Thanks for your advice.


One thing I'd suggest is that you know your definitions of all the key terms inside out because they can make a number of multiple choice questions out of one simple definition for example SHM or circular motion etc.
Constantly practice rearranging formulae and the relationships between them.
Good luck with your mock and let me know how it goes! :biggrin:


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Original post by saad97
One thing I'd suggest is that you know your definitions of all the key terms inside out because they can make a number of multiple choice questions out of one simple definition for example SHM or circular motion etc.
Constantly practice rearranging formulae and the relationships between them.
Good luck with your mock and let me know how it goes! :biggrin:


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Ok thanks.
Hey anyone explain to me about the magnetic field?
The circle with a dot or a cross to show the direction of the field or the current...
Teacher taught me if the current is going into the page then it's this...

What does she mean going into the page? Whats the purpose of the circle with a dot/cross
And she also mentioned about vectors too
(edited 9 years ago)
Reply 32
If the there is a cross in the circle then the field is going into the page ( think of a cross section of the back of an arrow head ) if there is a dot in the circle then the field is coming out of the page ( think of it as the tip of the arrow head )
That's all there is to it

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Reply 33
I can never get the correct answer using the left hand rule. How do you know which direction current is flowing? :/


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Reply 34
Original post by saad97
I can never get the correct answer using the left hand rule. How do you know which direction current is flowing? :/


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Are you finding the direction of current? Or are you already given it.
Original post by saad97
I can never get the correct answer using the left hand rule. How do you know which direction current is flowing? :/


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If you do FP4 in maths there is an easier way. Force = length times current cross field, or F = LIxB. If you don't do FP4 ignore this.
This gives the force pushing the wire.
Physics generally confuses me, I'm finding the concepts so hard to understand and so I don't do vey well on the mocks :frown:
Hey - could somebody possibly help with an A2 mechanics question (OCR physics A, newtonian world)
Really don't understand the markscheme.

Q2)b)ii)
http://www.ocr.org.uk/Images/144792-question-paper-unit-g484-01-the-newtonian-world.pdf

MS
http://www.ocr.org.uk/Images/142403-mark-scheme-unit-g484-the-newtonian-world-january.pdf
Reply 38
Original post by Makashima
Hey anyone explain to me about the magnetic field?
The circle with a dot or a cross to show the direction of the field or the current...
Teacher taught me if the current is going into the page then it's this...

What does she mean going into the page? Whats the purpose of the circle with a dot/cross
And she also mentioned about vectors too



By going into the page that is literally exactly what she means. Don't know how else to explain it to you!

The dot and cross are just symbols used to represent the direction of the magnetic field. My teacher taught me to remember it like this:

Imagine the magnetic field is an arrow that you throw when playing darts. If you see a cross, that's the magnetic field going INTO the page, so you can see the cross of the "tail" of the dart (not sure if that's the technical term for it but w/e). If you see a dot, that's the point of the dart coming towards you and so the magnetic field is coming OUT of the page towards you. Don't think I've ever heard the word vectors mentioned once when I was being taught it so don't know what she's going on about. Hope that helps!

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This shouldn't be hard. While I'm perfectly capable of answering the question, I just want to check a couple of things. Am I right to say that the normal contact force at A is 0? And just what is going on at B? At every other point on the circumference, I can see that either the weight or the normal contact force caused by a component of the velocity is sufficient as a centripetal force. However at B, both the weight and the velocity aren't in the direction of the drum's walls, so I can't see how the net force can be directed towards the centre of the circle (I can't even see how there can be a contact force), help?

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