OCR Physics A - G485: Fields, Particles & Frontiers of Physics - June 2012

Scroll to see replies

You're a bit mixed up with your terms.

Force acts up the page, this is why the electons accelerate upwards in the magnetic field region.
The conventional current is flowing left. Remember, electron flow is opposite to conventional current.

Flemming's LHR ALWAYS uses conventional current.

[Edit: to answer your last question, conventional current flows opposite to the direction of negative charge flow, and in the same direction as positive charge flow.]

This question gets me aswell. using Flemings Left Hand Rule, and Knowing the current direction is opposite to the direction of the electron (in this case to the left) how can you use Flemings left hand rule to get the force direction as we dont know the direction of the magnetic field? i dont understand

Reply 261

magdaplaysbass

Original post by stunnaman

You can work out the force by looking at the path of the electrons in the magnetic field. The electrons describe a circular path; so the force acts perpendicular to the electrons, towards the centre of their circular path (i.e. upwards.)
Now that you know the direction of the force and current, you can use Fleming's LHR to determine the direction of the magnetic field. :smile:

This was posted from The Student Room's Android App on my GT-S5830

Reply 262

coco739

What score would give the full 150 ums? just sizing up my chances :frown:

Reply 263

sugaris

Does anyone have the Jan 2012 paper and mark scheme? My teacher never gave it to me :frown:

Reply 264

wibletg

Original post by sugaris

Does anyone have the Jan 2012 paper and mark scheme? My teacher never gave it to me :frown:

It's on the front page of this thread :smile:

Reply 265

Mike93L

Original post by coco739

What score would give the full 150 ums? just sizing up my chances :frown:

Probably around 90 raw marks. The highest mark achieved in each paper range from 91 to 94.

(edited 11 years ago)

Reply 266

NerdyMcNerdNerd

Can anyone tell me if all of the questions in the "all g485 questions. part 1 & 2" attachments are relevant to our specification?

I don't wanna do something for ages if I don't have to know it!

Thanks very much :smile:

Reply 267

magdaplaysbass

Let's continue with model answers.

Describe the alpha-particle scattering experiment; and the evidence it provides for the chage, existence and small size of the nucleus (7 marks)

This was posted from The Student Room's Android App on my GT-S5830

Reply 268

shyro1000

dreading this :frown:

struggling in physics

Reply 269

Picture~Perfect

Original post by shyro1000

dreading this :frown:

struggling in physics

Is there anything in particular that you don't understand? Or want to go over?
I might be able to help explain a few things :smile:

Reply 270

t01

Original post by Toshiya

Does anyone have model answers (e.g. from a markscheme!) about how x-rays, PET scans, CAT scans, and contrast mediums work. In fact, any of the medical physics stuff - I know the basics but I'm really struggling to write what the mark schemes actually want.

I've uploaded some revision notes I made using mark scheme answers. It has some things on medical physics. Hope this helps.

Essay Type Questions.pdf75.2KB

Reply 271

Brap4k22DivideBy2

Original post by t01

I've uploaded some revision notes I made using mark scheme answers. It has some things on medical physics. Hope this helps.

Those essay questions look familiar. Weren't they for Jan 2012?

Reply 272

jedi-master

Hi, could anyone answer my question please?

If the area under the pd vs q (capacitor topic) is equal to the energy stored by the capacitor, then what does the gradient represent? 1/C?

Thx

Reply 273

Mathlete 4 the win

Original post by jedi-master

Hi, could anyone answer my question please?

If the area under the pd vs q (capacitor topic) is equal to the energy stored by the capacitor, then what does the gradient represent? 1/C?

Thx

Q= CV
C=Q/V

Depends how the graph is plotted.
If the graph is plotted with Q on the y-axis and V on the x-axis then the gradient is equal to C.

If it's plotted with V on the y-axis and and Q on the x-axis then the gradient is equal to V/Q.
Which is equal to 1/C.

Reply 274

t01

Original post by Brap4k22DivideBy2

Those essay questions look familiar. Weren't they for Jan 2012?

They're all from past papers so, yes, some of them will be from Jan 2012.

Reply 275

crazy1234

Original post by coco739

What score would give the full 150 ums? just sizing up my chances :frown:

Depends on the paper, but anything in the mid-80s is fairly safe for full UMS I think...

Reply 276

wibletg

Original post by crazy1234

Depends on the paper, but anything in the mid-80s is fairly safe for full UMS I think...

Yeah, with the exception of Jan 12 where I think it was 88 raw marks for 150 UMS?

I've not done that paper so I don't know how easy or difficult it was compared to the rest though :tongue:

Reply 277

Toshiya

Original post by t01

I've uploaded some revision notes I made using mark scheme answers. It has some things on medical physics. Hope this helps.

Oh wow, thank you! That's brill - thank you!

I've done some past papers today and I'm encouraged by the grade boundaries. Got 62 on one paper and thought it wasn't great but then realised this is actually a B which is higher than I need for a B overall!
As long as the grade boundaries aren't like January I should be safe. I think. I hope!

(edited 11 years ago)

Reply 278

Picture~Perfect

Original post by crazy1234

Depends on the paper, but anything in the mid-80s is fairly safe for full UMS I think...

Around 80 huh?
Thats pretty good it still leaves you with an error of about 15 marks.
I might have to make this my goal, I've never had full UMS before it would be a nice thing to accomplish :smile:

Reply 279

crazy1234

Original post by wibletg

Yeah, with the exception of Jan 12 where I think it was 88 raw marks for 150 UMS?

I've not done that paper so I don't know how easy or difficult it was compared to the rest though :tongue:

Damn that is high. Haven't done Jan 12 yet, so I didn't check the grade boundaries for it. It could be because of that extra 15 minutes we get, because its now 2 hours, so boundaries have gone up. Might be that or an easier paper as you said...