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AQA Physics PHYA4 - 20th June 2016 [Exam Discussion Thread]

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1st one

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Couldn't you just calculcate Energy for first capacitor, then energy for when it decreases, then minus biggest from smallesT?

Reply 1281

UsmanM

MCQ's were harder. Paper was okay. I think boundaries will be a bit higher than last years. Maybe 52 A, 47 B, 42 C?

Reply 1282

Mango Milkshake

Original post by Burnzi

How did you guys work out the time constant of the capacitor? I worked out the resistance then used that to get the time constant but then the next part of the question asked you to work out the resistance so I'm guessing you were supposed to do the first part a different way

yes, you use decay of charge equation with voltage

Original post by TheLazyGuy1

it is Y to X because the magnitude was -2F

magnitude can't be negative lol

Reply 1283

Yo12345

Was potential 5Q/8piEor and was the other potential -4GM/d?

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Reply 1284

rich1334

For the multiple choice with 2nc and -1nc you added 2nc to both didnt you? So it would repel by 4F? I wasn't so confident

Reply 1285

Craig David

1/g my friend. Not g

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Reply 1286

james2mid

Original post by Mango Milkshake

Daughter

Reply 1287

jovdawesome

Original post by Hattie28

I got 6.06x10^6 for something aswell :smile:

yessss i got 6.06x10⁶ aswell as g would be 4x greater

Reply 1288

Osmium

Original post by lucabrasi98

How can you guys have found the 6 marker hard? Haven't your teachers made you do past ISA's? Because I'm pretty sure I've basically seen that exact question in an ISA

We did this this year.

Reply 1289

Questioner1234

Original post by lucabrasi98

How can you guys have found the 6 marker hard? Haven't your teachers made you do past ISA's? Because I'm pretty sure I've basically seen that exact question in an ISA

I thought that was the easiest 6 marker of any past papers simply because I've done the experiment before but I'd think that if you haven't done it it would be very hard.

Reply 1290

cowie

MC was definitely more difficult.. Required many more calculations and had more little trip-up questions. On the other hand second B was pretty standard with only application/HSW questions posing much difficulty. I would expect grade boundaries to be average.
Also boundaries will no doubt be marginally lower due to the silly people completely missing the question over the 6 marker so we all have to thank the silly people in question :smile:

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Reply 1291

CourtlyCanter

Original post by duncant

what did people say for the effect when that guy recorded only half of T? was it (1/4)g?

I said the g (calculated in his investigation) is 4 times greater than what it should be as
T=2π x √(l/g)
T^(2)=4π^(2) x (l/g)
g=(4π^(2) x l ) / T^2

Therefore g is proportional to (1/T^2)

0.5 x 0.5 = 0.25
1/0.25 = 4 (Hence the effect results in the g calculated being 4 times greater than it should be.)

A little long-winded I know but I hope it makes sense.