# OCR Physics A G485 - Frontiers of Physics - 18th June 2015Watch

3 years ago
#661
(Original post by L'Evil Fish)
I just did that one, lost a mark there... Not sure why
That question also confused me for a while, but it's because the question states that the current through the circuit is constant.
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3 years ago
#662
(Original post by sagar448)
Oh I see, but then when would it be exponential?
when the current is not kept constant by the use of a variable resistor. usually current, charge and voltage decrease exponentially.
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3 years ago
#663
How do i convert 4 x 10^4 Vcm^-1 to V m^-1, explanation/ exaples too for understanding please; thanks.

Sorry solved.

1/1cm

Then it follows, 1 / 1x 10^-2 = 100 m
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#664
(Original post by Oraeng)
So why is it wrong if you do convert them if the units cancel out anyway?
It isn't

You probably converted them wrong
(Original post by FeelsToWaltz)
That question also confused me for a while, but it's because the question states that the current through the circuit is constant.
Yeah makes sense now
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3 years ago
#665
(Original post by boristeve)
when the current is not kept constant by the use of a variable resistor. usually current, charge and voltage decrease exponentially.
Oh I see, but current decreases exponentially when charging and voltage and charge increase exponentially. Just to make sure you don't mess up.
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3 years ago
#666
(Original post by L'Evil Fish)
It isn't

You probably converted them wrong
1.7cm = 0.017m
6.5cm^-1 = 0.065m^-1

am I missing something?
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3 years ago
#667
Hello does anyone know where to get the answers for the end of chapter questions in the OCR textbook?
Why they're not in here Idk

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#668
(Original post by Oraeng)
1.7cm = 0.017m
6.5cm^-1 = 0.065m^-1

am I missing something?
Yeah the 6.5cm^-1 would go to 650
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3 years ago
#669
(Original post by Leechayy)
Hello does anyone know where to get the answers for the end of chapter questions in the OCR textbook?
Why they're not in here Idk

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these ones? sorry its a txt file, the pdf was massive and too big
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3 years ago
#670
Can anyone explain the shape of the graph for question 4bii) please from the paper below

http://www.ocr.org.uk/Images/81115-u...s-specimen.pdf

Thanks.
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3 years ago
#671
(Original post by boristeve)
these ones? sorry its a txt file, the pdf was massive and too big
It's okay
Thankss

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3 years ago
#672
(Original post by boristeve)
is it sinuisoidal?
No, it only consists of straight lines. The emf is zero before the coil enters the field, and then whilst in the field the emf stays constant (constant change of flux). The bit I don't get is that it says on the mark scheme that there should be a negative emf (the emf apparently changes direction half way through the motion) But the direction in which the flux is cut is always the same, so I don't get that?
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3 years ago
#673
(Original post by ReeceG46)
No, it only consists of straight lines. The emf is zero before the coil enters the field, and then whilst in the field the emf stays constant (constant change of flux). The bit I don't get is that it says on the mark scheme that there should be a negative emf (the emf apparently changes direction half way through the motion) But the direction in which the flux is cut is always the same, so I don't get that?
I think it is to do with Lenz's Law.
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3 years ago
#674
Hey everyone. New to the thread. Just curious: is anyone else, in a sick and twisted way, looking forward to this exam?
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3 years ago
#675
(Original post by The Room Student)
Hey everyone. New to the thread. Just curious: is anyone else, in a sick and twisted way, looking forward to this exam?
Lol no

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3 years ago
#676
(Original post by boristeve)
these ones? sorry its a txt file, the pdf was massive and too big

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3 years ago
#677
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3 years ago
#678
(Original post by Leechayy)
Lol no
Haha, sounds weird I know, but the low grade boundaries just make me feel kinda chilled about it!

There's a load of stuff to learn, but once you've grasped it, most questions are quite friendly I think...
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#679
(Original post by The Room Student)
Hey everyone. New to the thread. Just curious: is anyone else, in a sick and twisted way, looking forward to this exam?
Yes !!!
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3 years ago
#680
(Original post by Leechayy)

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here you go
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