OCR B (Advancing Physics) G492, 25th May 2012 Afternoon

OP

As of June 2011, the front of the question papers say you need a protractor. Holy **** I genuinely don't think I own one.

Reply 122

Original post by When you see it...

As of June 2011, the front of the question papers say you need a protractor. Holy **** I genuinely don't think I own one.

WHAT???!!!!

Reply 123

Oglogski

Original post by When you see it...

As of June 2011, the front of the question papers say you need a protractor. Holy **** I genuinely don't think I own one.

Only required for scale diagrams to work out vectors, and they always say "by scale drawing or some other method" so I just use pythag/basic trig.

Basically, you don't need one! :smile:

Reply 124

master y

12

People people stop panicking!! OK... now im starting to panic.... :O

Reply 125

Original post by master y

People people stop panicking!! OK... now im starting to panic.... :O

Analogue, uncertainty is ±5%

Digital, Uncertainty is ±0.01%

Can you anybody help me. I dont understand how this percentage uncertainty was worked out from the prereleased. please
EDIT someone worked it out and i dunno how they did it please help

(edited 11 years ago)

Reply 126

Original post by Education_1

Analogue, uncertainty is ±5%

Digital, Uncertainty is ±0.01%

Can you anybody help me. I dont understand how this percentage uncertainty was worked out from the prereleased. please
EDIT someone worked it out and i dunno how they did it please help

The digital voltmeter measures to 2 decimal places so the uncertainty will be ±0.005, i dont understand how they worked out the percentage uncertainty though becuse you dont know the value measured to calculate the percentage uncertainty

the uncertainty of the analogue voltmeter will be ±1 be cause the smallest intervals on the scale are in 2's

Hope this helps

Reply 127

OP

Original post by Oglogski

Only required for scale diagrams to work out vectors, and they always say "by scale drawing or some other method" so I just use pythag/basic trig.

Basically, you don't need one! :smile:

Okay thanks.

Original post by KoalaKim

The digital voltmeter measures to 2 decimal places so the uncertainty will be ±0.005

I forgot to mention that my physics teacher said the uncertainty for the digital ammeter is +/-0.01 A which makes more sense to me.

Reply 128

Original post by KoalaKim

The digital voltmeter measures to 2 decimal places so the uncertainty will be ±0.005, i dont understand how they worked out the percentage uncertainty though becuse you dont know the value measured to calculate the percentage uncertainty

the uncertainty of the analogue voltmeter will be ±1 be cause the smallest intervals on the scale are in 2's

Hope this helps

oh thank you :smile:

also i thought my teacher told me the uncertainty of the digital will be 0.01 (you dont half it since you dont see the division) thought im unsure if he is correct because he cant teach and he does make mistake so im not sure :s-smilie:

EDIT: someone else confirmed it :smile:

that reassuring :smile:

Thank you

(edited 11 years ago)

Reply 129

Romeuo

Original post by Education_1

oh thank you :smile:

also i thought my teacher told me the uncertainty of the digital will be 0.01 (you dont half it since you dont see the division) thought im unsure if he is correct because he cant teach and he does make mistake so im not sure :s-smilie:

EDIT: someone else confirmed it :smile:

that reassuring :smile:

Thank you

0.01A would be the resolution of the digital ammeter. Half it for the absolute uncertainty

Reply 130

matty b

Original post by KoalaKim

The digital voltmeter measures to 2 decimal places so the uncertainty will be ±0.005, i dont understand how they worked out the percentage uncertainty though becuse you dont know the value measured to calculate the percentage uncertainty

the uncertainty of the analogue voltmeter will be ±1 be cause the smallest intervals on the scale are in 2's

Hope this helps

it's cos it rounds up or down, so the highest/lowest values are +/- 0.005, right?

Reply 131

Original post by Romeuo

0.01A would be the resolution of the digital ammeter. Half it for the absolute uncertainty

No you dont half it in this case according to my teacher! yes it would but 0.01 according to him is the uncertainty

EDIT:he is right guys so make sure in the exam you write 0.01A as uncetainty
have a look at
http://www.youtube.com/watch?v=1dTn2pt5PuA (1.14)

(edited 11 years ago)

Reply 132

Original post by Education_1

No you dont half it in this case according to my teacher! yes it would but 0.01 according to him is the uncertainty

EDIT:he is right guys so make sure in the exam you write 0.01A as uncetainty
have a look at
http://www.youtube.com/watch?v=1dTn2pt5PuA (1.14)

so what is the uncertainty of the analogue one?? 2??

Reply 133

master y

12

Can anyone tell me why it is particularly important for an ammeter to have 0 resistance for LARGER currents being measured?? (3)

(edited 11 years ago)

Reply 134

Original post by master y

Can anyone tell me why it is particularly important for an ammeter to have 0 resistance for LARGER currents being measured?? (3)

An ammeter is placed in seris so if it has a high resistance then this will change the current because V = IR, and if voltage remains constant and R increases then i will decrease so its imprtant to have a small R in an ammeter

Reply 135

master y

12

Original post by KoalaKim

An ammeter is placed in seris so if it has a high resistance then this will change the current because V = IR, and if voltage remains constant and R increases then i will decrease so its imprtant to have a small R in an ammeter

but why are larger currents in the circuit affected more than smaller currents? :>S

Reply 136

OP

Original post by master y

but why are larger currents in the circuit affected more than smaller currents? :>S

Oh yeah, I saw that question. The mark scheme said something like 'for larger currents, power dissipated as heat is more as P=VI=I^(2)R' but I put 'larger currents are larger to begin with, therefore (as they decrease by the same proportion) the magnitude of the decrease is higher'.

Reply 137

Original post by KoalaKim

so what is the uncertainty of the analogue one?? 2??

nope as you said 1 ... its just for digital that is different

Reply 138

OP