OCR PHYSICS B G495~ 18th June 2015 AM ~ A2 Physics

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Reply 220

STATER

Original post by falconinni

You used pV=NkT, rearranging for N/V. You then had to convert cm^3 to m^3

What was your N?

Reply 221

urz13

Fairly happy with that - I nailed section C (I got 0.027m too!), section B and A were decent on the whole. Had no clue about the induction 4 marker but put something down so I'll hopefully pick up a mark or two there, also made a couple of silly errors on section A bit hopefully I've done enough overall - I need about 130UMS in this paper for an A* aproximately.

Reply 222

Mutleybm1996

Original post by falconinni

You used pV=NkT, rearranging for N/V. You then had to convert cm^3 to m^3

Damn
I set V=1 and solved for N....
Grrrr

Reply 223

STATER

Oh so the answer was N/V? I thought it was just V

Reply 224

STATER

Original post by Mutleybm1996

Damn
I set V=1 and solved for N....
Grrrr

I think you are correct actually. Just had to convert to cm.

Reply 225

Mutleybm1996

Original post by STATER

I think you are correct actually. Just had to convert to cm.

Whoops
Oh well
-1 mark there

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Reply 226

STATER

For induction I said that rotation causes an opposing current to be induced. Stopping rotation stopped this 'back emf' increasing net current.

Reply 227

falconinni

Original post by Mutleybm1996

Damn
I set V=1 and solved for N....
Grrrr

Setting V to 1 should get the same answer

Reply 228

falconinni

Original post by STATER

What was your N?

I can't remember :/

Reply 229

Lord-Febreeze

Original post by STATER

I think you are correct actually. Just had to convert to cm.

No I'm sure it was N/V, if they wanted you to say V=1 they would have included it when they told us the values of P and T etc.

Reply 230

urz13

Original post by STATER

For induction I said that rotation causes an opposing current to be induced. Stopping rotation stopped this 'back emf' increasing net current.

That sounds correct, definitely. I just couldn't think straight about it in the exam and so I only got the bit about an opposing current being created, which is annoying, so at least -2 marks there for me. Well done though, how did you find the whole paper?

Reply 231

STATER

Original post by Lord-Febreeze

No I'm sure it was N/V, if they wanted you to say V=1 they would have included it when they told us the values of P and T etc.

Its per cm^3 if I recall correctly which means v=1cm

Reply 232

STATER

Original post by urz13

In general it was exactly what I wished for. All the extensive preparation payed off and there weren't many surprises.

Reply 233

Mutleybm1996

Original post by STATER

Its per cm^3 if I recall correctly which means v=1cm

So I would need to convert to cm?

Reply 234

STATER

Harder or easier than 2014? I think section C was a bit trickier, induction was harder. Radiation was easy. Electric fields was non standard so a bit trickier. Maybe boundaries might fall by one mark or stay the same?

(edited 8 years ago)

Reply 235

Aeglor

FML I dropped perhaps 6 marks in most of the paper but didn't see the double page spread at the end........

Reply 236

Minecraft27

I got N to be 2.4x10^9 or something.

Anyone else get a resolution of 5.2x10^-7 and 30,000 lenses covering the eye?

Reply 237

rohanpritchard

Don't remember the question, something to do with a rotor in a stator where something increases (might have been potential difference but I'm not sure). It asks what happens to the speed of rotations? I put that although the force on the rotor will increase, the speed of rotations does not due to the fact that the question stated that the current remains the same and I figured this meant that the poles don't switch any quicker so it can't spin any faster... Does anyone agree/disagree? And does anyone actually remember the question properly? :smile: