A2 Physics | Post your doubts here

[user]

Help me also for s05 6b)

I'm confused... my book says the applied emf and the induced emf across the secondary coil are out of phase by 180 (pi)..
and the answer to question b iii) is 90 (pi/2) .. why is this so?
Do u think my book has an error?View attachment 9240 is this correct? (Sorry for bad drawing)

and it's correct btw

 

[SkyPilotage]

Assalamoalaikum wr wb!

on thursday i think,you asked a question about the graph for diode/rectification one, and u said you didnt et it..sorry cudn't postsome pic that day..
here's it:
hope it helps...
View attachment 9241



http://www.flashscience.com/electricity/smoothing.htm

^check this link to see why there's a flat line in the graph...there'll be a part...when one set is working and the other two are not and vice versa..

why is the rectification max voltage less than the ac input?

 

[namename]

before that tell me one thing, plz..do u take maths p3? differentiation part..?

I gave full A math last Oct/nov and got A*. will give Furthermath this time. why?>

 

[SkyPilotage]

I gave full A math last Oct/nov and got A*. will give Furthermath this time. why?>

apparently he wants you to differentiate magnetic flux with respect to time.
Emf = d (flux / time)

 

[namename]

and it's correct btw

Hmm.. that means my book is wrong?

 

[namename]

apparently he wants you to differentiate magnetic flux with respect to time.
Emf = d (flux / time)

I think it would be emf= -d(flux/time)

 

[user]

apparently he wants you to differentiate magnetic flux with respect to time.
Emf = d (flux / time)

assalamoalaikum wr wb!

exactly...

I gave full A math last Oct/nov and got A*. will give Furthermath this time. why?>

ok so i just wanted to know u know differentiation or not

u asked why is it so...
so u know that induced emf is -d(phi)/dt that is basically the gradient of the first graph...of flux against time...

that's actually a sine curve...when u differetiate you get cos x
and since induced emf is -d(phi)/dt , it'll be -cos x and hence the graph you drew...

 

[user]

I think it would be emf= -d(flux/time)

yup it is

 

[namename]

assalamoalaikum wr wb!

exactly...


ok so i just wanted to know u know differentiation or not

u asked why is it so...
so u know that induced emf is -d(phi)/dt that is basically the gradient of the first graph...of flux against time...

that's actually a sine curve...when u differetiate you get cos x
and since induced emf is -d(phi)/dt , it'll be -cos x and hence the graph you drew...

Yea that is exactly how i drew it out.
but my book is saying that the applied emf is out of phase with the induced emf by pi (180 degrees) - in case of transformer
Thats why i get confused

 

[user]

Hmm.. that means my book is wrong?

it shud be
or probably it means something else...i mean there' must be something else there..!! which book btw?

and after drawing the graph when you compare, you can find the phase difference..

 

[namename]

it shud be
or probably it means something else...i mean there' must be something else there..!! which book btw?

and after drawing the graph when you compare, you can find the phase difference..

International A/AS level physics by chris mee, mike crundell, brian arnold and wendy brown
Hodder education

 

[user]

International A/AS level physics by chris mee, mike crundell, brian arnold and wendy brown
Hodder education

i have the same book can you tell me which page?

 

[smartangel]

http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_w07_qp_4.pdf
Q6b i..PLZ HELP!!

 

[namename]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_qp_4.pdf
Q6b i..PLZ HELP!!

Think of motor (pinch) effect of two wires carrying current in the same direction.

 

[user]

why is the rectification max voltage less than the ac input?

it's due to the voltage drop across the diode...it's something like that..i don't remember which year question was it...
but i remember I drew it less...and probably did so from mark scheme....
i just googled it...and it's says something abt the voltage drops..i do get a rough idea..do u?

 

[smartangel]

http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_w07_qp_4.pdf
Q6 b ii..why have they used 2x pi x r rather than l as 9.4??

 

[hassam]

http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_w07_qp_4.pdf
Q6 b ii..why have they used 2x pi x r rather than l as 9.4??

because force is experienced along the whole circumference of the wire

 

[hassam]

International A/AS level physics by chris mee, mike crundell, brian arnold and wendy brown
Hodder education

brother u are correct ....emf in primary coil and emf in secondary are 180 degree out of phase........the question asked about current and emf in secondary coil which is ov corass 90 degree out of phase

 

[hassam]

well for q7 b http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w09_qp_41.pdf

 

[hassam]

well k i used pTIMES DELTA V......and got the anser......bt oe doubt...as we knw internal energy of ideal gas is 3/2 PV,,.....why it cnt be used here.....cnt undrstnd why it gives the rong ansa'
http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w09_qp_42.pdf and i cnt understand why ms says insufficient info for answering the question relating to temp. change cos......we can use 3/2 pv to anser this