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OCR Physics B G491 20th May 2013

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Guys for question 4(b) unfortunately, the answer is not 15mS, it is 30mS. That is because Total conductance across parallel circuits is equal to them being added together. Therefore, 15+15= 30mS. I do hope others got that one right, because many seem to fail to understand why it ISNT 15mS.

Resistance adds up in series and conductance adds up in parallel curcuits. Therefore the answer is 15mS

Reply 141

zcQ

Original post by jelmes96

Resistance adds up in series and conductance adds up in parallel curcuits. Therefore the answer is 15mS

Yep I got 15mS

Reply 142

RevisionEssence

Original post by Paribas01

Yep I got 15mS

Hang on, were the points A and B between all conductors? I thought it was only at the parallel part...

(edited 10 years ago)

Reply 143

jelmes96

Original post by jelmes96

I said something like "Concrete is tough when a compressive force is exerted onto the composite, beause it has an amorphous structure, not allowing the grains to slip past each other, however as concrete is a composite, (mixture), the material is not chemically bonded and there are no inter molecular forces, allowing the material to fracture suddenly with out deforming plastically when a tensile force is exerted.

Can someone comment on this guys?

Reply 144

Josh-B

Original post by RevisionEssence

Hang on, were the points A and B between all conductors?

Pretty damn sure they were

Reply 145

jelmes96

Original post by RevisionEssence

Hang on, were the points A and B between all conductors?

yep

Reply 146

King Hotpie

Original post by RevisionEssence

Hang on, were the points A and B between all conductors? I thought it was only at the parallel part...

They bloody well better have been

Reply 147

Dan1300

For the question about the relationship on the graph i put the two variables increase uniformly. Will this get me the mark even though i didn't put directly proportional?

Reply 148

RevisionEssence

Ah damn, so I lost 5 marks in total. Oh well :P Good luck guys! xD Hope you all got your A's

Reply 149

RevisionEssence

Original post by Dan1300

For the question about the relationship on the graph i put the two variables increase uniformly. Will this get me the mark even though i didn't put directly proportional?

Yeah you'll get the mark :smile:

Reply 150

metaltron

Original post by jelmes96

Can someone comment on this guys?

You might get a mark for mentioning an amorphous structure. Do you think the ms explanation is good for the 4 marks?

Reply 151

snailfur

Can anyone upload a copy of the actual paper?

Reply 152

King Hotpie

Original post by snailfur

Can anyone upload a copy of the actual paper?

I second this motion

Reply 153

Dan1300

We need somebody to upload the paper and give the worked solutions like that maths guy "arsey" does

Reply 154

Dan1300

I cant wait until i get my results thats too long :biggrin:

Reply 155

jelmes96

Original post by metaltron

You might get a mark for mentioning an amorphous structure. Do you think the ms explanation is good for the 4 marks?

Why just one mark? It was a good explanation :O

Reply 156

metaltron

Original post by jelmes96

Why just one mark? It was a good explanation :O

I'd say 2/4 for the slip part as well. However, I'm not sure as I haven't seen the mark scheme and material mark scheme are random sometimes.

Reply 157

joshdrew2

I thought the curvature one was 7.5D as the formula would have been 1/f - 1/u but u was negative which turned it to 1/f +1/u

Reply 158

fattail95

For 9)b)iii] I put:

Advantage: Trees dont have to be cut down to make paper books.
Disadvantage: The devices have to be manufactured, which may involve burning greenhouse gases and releasing CO2.

Fair enough?

Reply 159

Crabbiey

For the axe head question - you couldn't put tough or strong and have different marking points for them - they are the same thing and the paper stated that steel has a high density, which means it is strong/tough. Meaning the markscheme won't accept it. The only remaining property of metals is ductile (metals have three properties), this is useful as it means steel can be shaped without loosing its strength. It can't be malleable as that would mean steel would loose its strength.

For that ebook question I said:
Advantages:
Reduces number of trees cut down.
Ebooks are easier to transport.
An electronic book is cheaper.

Disadvantages:
People are opposed to Ebooks.
Ebooks put bookshops out of buisness/lower their income as books shops sell paper books.
Not all places have Wi-Fi and it may not be free.
Ebooks are much more expensive than a paper book.
Not everyone knows how to use an Ebook.

Another one I thought of was that Ebooks could require computers to be charged and not everyone has a computer.

I said concrete had a ceramic structure - I was running out of time and rushing. Though amorphous and ceramic should both get marks, they're just dependent of cooling time.