Edexcel Physics 6 june 2002

can someone with a markscheme post the answer for Q1 part C for june 2002 phy6?

Outline briefly how a Van de Graaff generator can accelerate electrons to very high energies.

Reply 4

zoidberg

can someone with a markscheme post the answer for Q1 part C for june 2002 phy6?

Outline briefly how a Van de Graaff generator can accelerate electrons to very high energies.

I havent got the markscheme... but would you like me to give it a go anyway?

Reply 5

sure, its 3 marks. i know how a VDG generator works but just cant think of how to explain it to be worth that much in that context

Reply 6

ok here goes:

The earthed needle places electrons on the belt, which subsequently makes the belt negatively charged. This charge is then removed at the top by electrons flowing off a different needle into the sphere. Consequently, the charge builds up as more and more electrons are added to the sphere until the rate of addition of electrons equals the rate of removal of electrons through insulation leaks etc. There is a filament which is connected to the sphere, which results in it becoming negatively charged too. Once the charge has built up to a certain level, electron are ejected from this filament and are repelled by the negative charge of the sphere, consequently resulting in the acceleration of the ejected electrons to very high energies. :smile:

how is that for ya? :smile:

some feedback would be nice to know where i would lose the marks in ur opinion :smile:

Reply 7

sounds good, when you say the electrons are ejected is that through a spark? that's all i associate van der graaffs being any use for :tongue:

thx

Reply 8

zoidberg

sounds good, when you say the electrons are ejected is that through a spark? that's all i associate van der graaffs being any use for :tongue:

thx

lol... in this case i dont think it would be seen as a spark... i think it would be just like in an CRT...

Reply 9

hmm the diagram still confuses me, the filament thing connected to the van der graaff, doesnt that just provide the accelerating force and doesnt actually emit electons? i thought the electron gun did that.

Reply 10

zoidberg

hmm the diagram still confuses me, the filament thing connected to the van der graaff, doesnt that just provide the accelerating force and doesnt actually emit electons? i thought the electron gun did that.

yeah you are right... why is that filament there then? the sphere does most of the accelerating force...

Reply 11

if you look on the jan04 paper... they have the same diagram but without the filament (but its the positive one)... confusing :s

Reply 12

hmm confusing, oh well if it comes up again tomorrow should be able to bumble through enough to get a few marks

Reply 13

zoidberg

hmm confusing, oh well if it comes up again tomorrow should be able to bumble through enough to get a few marks

yup thats the mentality :biggrin:

most people dont need high marks in this anyway :smile:

i think 60% should guarantee me an A :smile:

Reply 14

yeah me too hopefully, got a high 90% for as and as far as i know did ok on phy4/5. hardly done any revision for tomorrow, dont really know what there is to revise, most of the questions you can just make educated guesses at and theres quite a lot of easy marks on maths/base units crap :smile:

Reply 15