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aqa A 10 revision thread

Im just interested to see who else is facing this paper! ok question time

this one confused me for a little while

Dry air ceases to be an insulator if it is subjected to an Electric Field strength of 3.3kV/mm or more

E=V/R field strength=potential/radius of sphere

the dome of a van de graaff generator has a radius of 0.20m. Calculate the maximum potential of this dome in dry air

b) two high voltage conductors are connected to a small sphere
they trasmit a.c of rms 100kV through the sphere

calculate the maximum diameter of the sphere necessary to ensure the surrounding air does not conduct.

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Reply 1

fluffyduck

Im not sure if these solutions are right but im sure the questions wont be this hard (but im doing Phy B):

A)
V=Er
3.3 kV/mm = 3300 V/mm = 3300000 V/m
So Vmax = 3300000 x 0.2 = 660000 V = 660 MV

b)
V = 100000 V
E = 3300000

r = V/E = 100000/3300000 = 0.03m (rad) so diameter =0.06m

Im not sure about part b). where are the questions from?

Reply 2

junners

I got a different answer for the second part.

B)

Peak voltage = RMS x square root of 2 = 141421V

E = 3300000

r = V/E = 141421/3300000 = 0.0429m (radius)

Therefore diameter = 0.0857m= 85.7mm (3sf)

Reply 3

Frogsofhope

its from jan 04 paper, i think you are both wrong let me just check

a) v=ER=3.3x10^6 x 20 = 660kv (not MV fluffy duck k for 1000, M for 1000000)

b)peak voltage= rms x root2 = 140kV

min radius = 140/3.3kV = 42.4

diameter=85mm

actually by the looks of it junners got it right, wel done :smile:

anyone got any more questions?

Reply 4

Frogsofhope

lessthanthree

I'm doing it. I'm considering winging it in favour of revising chemistry that I have the next morning.

I feel like I've buggered up significantly so as to negate the effects of revision.

i tried to revsie chem to get a break from physics, because i buggered up physics mod 4+5 , but I cant get to grips with chem5 and synoptic seems impossibly hard, seeing as i muddled through chem AS with 2 retakes and leaning things parrot style, and picked up little understanding/ways to adapt it to puzzles. Plus there seems to be far too much parrot style learning of colours, equations etc to pick up in just 1 weekend!! :eek:

Reply 5

junners

marisad_uk

What was the general reaction of your school to Module 4 Physics? (Specifically section B) Everyone at my school found that really hard ... I'm hoping to make up for lost ground in the Module 10. I reckon that Module was way too descriptive!

I've tried to understand Chemistry as I've been going along, because I never learning like learning by rote. However, with colours of transition metal complexes, I'm afraid there's no logic to it at all! The way I've set about trying to learn it is by placing all of them in a table, and then trying to learn the position of all the colours on the table.

Reply 6

Laffo

The 3 people who did mod 4 in my school found it hard, where as i found it really easy compared to the previous ones... I did do quite a bit of cramming before hand!

Im not looking forward to this exam. Altho it is my last so in a way i am :cool:

Reply 7

fluffyduck

OOps i dont know how i wrote MV instead of kV

Reply 8

Ventricles

*waves* i'm doing it too! :smile:

I dont think it should be too bad, its just alot of the questions make you really think about applying your knowledge to situations rather than just plug no.s in........ i dont like thinking too much :biggrin:

lol

Reply 9

Frogsofhope

junners

only me and my best mate do physics at my school lol! I looked at her afterwards and she just shook her head and we agreed that DID NOT GO WELL!

Reply 10

mr_shoe_uk

I found unit 4 hard, but I found all the past papers of it hard too.

Strangest question was writing Newton's Law in words.

Some of the synoptic past papers seem way easier than others. I actually did the one with thet Van Der Graaf question this morning, and it was definitely one of the harder papers!

Reply 11

gemm

im not looking forward to this exam at all!

i agree that this exam involves a lot of hard thinking :redface:

, it usually takes me a while to take in each question and get my head around it

Reply 12

Frogsofhope

gemm

im not looking forward to this exam at all!

i agree that this exam involves a lot of hard thinking :redface:

, it usually takes me a while to take in each question and get my head around it

hmm strange, these synoptic papers seem easier than mod4 and to have less thinking, to me anyway. :confused:

Reply 13

Laffo

Im not too bad on the maths for these, im just having trouble remembering things like spectra emission etc... dont like the writing questions :frown:

Maths is definatly my strong side of physics tho :cool:

Reply 14

gemm

hmm strange, these synoptic papers seem easier than mod4 and to have less thinking, to me anyway.

i suppose it depends how you think,
i find it harder because it involves bringing together different areas of the syllabus in 1 question, and applying the physics we've learnt to real situations

Reply 15

Ventricles

Maths is definatly my strong side of physics tho

oh me too! i'm not very good at the writing explanation qu's :frown:

i find it harder because it involves bringing together different areas of the syllabus in 1 question, and applying the physics we've learnt to real situations

i agree, i think its more tricky as its not clear cut as to what you need to use, you have to think about which parts you need and combine all the methods etc....... :eek:

But at least my exams are all over after this! :biggrin:

Reply 16

Frogsofhope

Ventricles

oh me too! i'm not very good at the writing explanation qu's :frown:

i agree, i think its more tricky as its not clear cut as to what you need to use, you have to think about which parts you need and combine all the methods etc....... :eek:

But at least my exams are all over after this! :biggrin:

me three once i figure out what eqn to use im away, i hate the writing questions, may just have to learn a few of them parrot styleeyy as to what gets the marks and what doesn't, as in practise i tend to ramble on about vaguely related things and not hit those key words to get the marks.

P.S hi gemm notice your siggy said you might be going to leeds, you never know we may bump into each other, although its a massive place, the TSR lot should have a get together- has anyone posted that as an idea on the leeds board yet? will go check now

Reply 17

junners

That's a bit of a relief! I thought our school was the only one who found that Module 4 hard. I reckon it's by far, one of the hardest I've done. I really didn't expect that many descriptive questions! I'm really bad at those!

On a side note, I'm hopefully going to Leeds as well!

Reply 18

corkskrew

saturday night and i'm sitting in a dimly lit room with a fan on (it's a sweltering 32C at the moment) struggling with speed=distance/time equations. long live the synoptic module. its a wonder i managed the stuff firsttime round, dont know why they think i can do it now....

Reply 19

xelprep

tomorrow i'm gonna be revising physics unit 10 all day. i messed up unit4 really bad :/ i think unit 7 went ok though - hopefully. i was so disappointed with unit 4 because all the past papers i found ok for written but hard on multiple choice. but in exam i think multiple choice was a bit easier. i thought all the past papers had standard questions then this exam was really different to me :/

i hope i get 65% for a B overall!