CCEA A2 Physics practical

capacitor capacitance and time constant?

i got 39 for the 1st time constant (0.37 % I and 0.37x0.37 for 2RC and averaged) for 4 marks i hope

and 12 for 2nd

got a capacitance of 1150 overall if i remember right

Didnt know what to say for the oscillation y intercept question tho

Reply 2

Original post by Aj2001brah

same - got 38s for first one and 12 for 2nd - I did the exact same thing for averaging except i did 1 more just to be safe

aah - they pulled a sneaky on you with the oscillation one - they were actually asking about the x intercept not the y intercept - the answer was it is equal to the original length of springs

it seems i fcked up on the last one then - a guy in my class said he also got 1200 for it

i got 90 somehow - this is what I did 1/(12/33000)= 1/C2 + 1/115*10-3

also what did you get for capacitance of the first capacitor? - as you can see I got 0.00115F

(edited 4 years ago)

Reply 3

also do you remember what you got for the P constant? - I remember dividing 4 pi^2 by the gradient to get 10 something

(edited 4 years ago)

Reply 4

hey man u still there?

if you are how'd you find today's test?

Awful really tbh lol

Original post by Aj2001brah

Awful really tbh lol

dude, same
it went absolute sh!t for me - esp the last few questions

what did you draw for the shape of the wave? - I got something resembling a hill - also what did you get for timebase? i got 5.55*10-5

Reply 7

btw how were you on time? I had to rush both practicals because of how slow i am

Reply 8

Physics A2 Practical today was really hard, few of my answers if anyone wanted to compare:
zero error: 0.16mA
timebase 50uscm-1
frequency: 1000Hz
CRO wave 2: 1/2 of a full wave (hill shape)

Reply 9

Science22

Got the same as you besides the zero error. I got 0.07mA. How did you calculate yours?
I just took the x intercept and divided that by my resistance

Also, what was your %uncertainty in cross-sectional area? I think I got 3.8% but wasn't sure if it was right

(edited 4 years ago)

Reply 10

yeah i used 4200 ohms instead of my own calculated resistance but I did exactly the same except that

Original post by Science22

Got the same as you besides the zero error. I got 0.07mA. How did you calculate yours?
I just took the x intercept and divided that by my resistance

Reply 11

I thought the zero error was the reading on the ametwr when v = 0 ie y intercept

Got 0.08mA from subbing in values to y=mx+c and rearraging for c

Reply 12

Original post by Benkxnnedy

Physics A2 Practical today was really hard, few of my answers if anyone wanted to compare:
zero error: 0.16mA
timebase 50uscm-1
frequency: 1000Hz
CRO wave 2: 1/2 of a full wave (hill shape)

hill shape gives me a relief; had the same pretty much
got 990Hz for frequency (so pretty much the same)
and got 5.5 (recurring) *10-5 for the TBS - I found the period by 1/1500 and then divided it by 2 and then divided it by 6.6cm (which was what appeared to be the length of half of the wavelenghts)
didn't get the zero error at all - i tried dividing y by the gradient - but something wasn't making sense

Original post by Science22

i just sort of extrapolated and guesstimated for the y intercept - obviously not what they wanted but i hope i can get a quality mark at least

i think i got 4.2% for uncertainty - i think i added %U of gravity that's why mine is higher

did you guys add the %U for gravity? I wasn't sure since 9.81 is a constant but i still did .01/9.81 *100 and then added that to the other uncertainties

(edited 4 years ago)

Reply 13

For the % uncertainty i did

2 x uncertainty for diameter + uncertainty in height + uncertainty in speed i think

for the log graph was the value you needed the gradient or the x intercept ? the one where it gave L0

(edited 4 years ago)

Reply 14

Original post by Aj2001brah

For the % uncertainty i did

2 x uncertainty for diameter + uncertainty in height + uncertainty in speed i think

do you think we were supposed to + uncertainty of 9.81 ms-2 (g)?

Reply 15

Got 42.5 for the y intercept and I didn’t use the % uncertainty for g because it didn’t give us one, I got 3.6ish% for error and something x10-4 for the CSA

Reply 16

no defo not i dont think

Reply 17

well that sucks - they really should have made that more clear

Original post by Benkxnnedy

Got 42.5 for the y intercept and I didn’t use the % uncertainty for g because it didn’t give us one, I got 3.6ish% for error and something x10-4 for the CSA

Original post by Aj2001brah

no defo not i dont think

also what did you guys get for the absolute uncertainty of the resistor? - I got like 435 ohms

Reply 18