Physics: Post your doubts here!

[confused123]

hi bro,

AoA wr wb

plz explain this solution

from where did u took this question ? is this answer really correct. i learned the formula in the cambrdige book which says in this case => AB/ AC into Eo i.e .65/1 into 12 = 7.8 Volt.

but here i see a different situation where first we divided ab length with total length and then multiplied with the total resistance of the wire. this gave us resistance across AB wire,

then we used this resistance to find the unknown e.m.f. of the test cell is this whole formula correct in the image?

 

[waleedsmz]

from where did u took this question ? is this answer really correct. i learned the formula in the cambrdige book which says in this case => AB/ AC into Eo i.e .65/1 into 12 = 7.8 Volt.

Well I think your formula only works if there is no other resistance in the circuit ( like the 20 ohms of internal resistance ) ... Since the whole of the line would actually have a P.D. of 12 V so AB/AC into 12... This example is actually somewhere on the site's revision pages. The last one in the D.C. area right here: http://www.xtremepapers.com/revision/a-level/physics/dc_circuits.php

Check my previous reply if you need more details. : )

 

[confused123]

Can anyone please explain this question from paper 2?

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s11_qp_21.pdf
Q number 5 part B

maximum current will be possible when the voltage across 6 ohm resistor equals to driver cell voltage or when there is least resistance in the circuit. i.e 12, when its 12, I =V/R ,
12/6 = 2 A .
Minimum will be zero . i am not sure bout this but maybe when the jockey is move towards the extreme position then the voltage or resistance might bcm zero then current will be zero as well :/ plz someone else clarify. Thanks

 

[confused123]

Two solid substances P and Q have atoms of mass MP and MQ respectively. They have NP and NQ atoms per unit volume such that NP= NQ. It is found by experiment that the density of P is greater than that of Q.

Which of the following deductions from this experiment must be correct?

A MP > MQ

B NP > NQ

C MPNP > MQ NQ

D MP/NP = MQ/NQ

A? maybe experimental error which caused wrong mass to be calculate which resulted in difference in densities? caz atoms atoms per unit volume will remain same..share the correct option

 

[confused123]

Well I think your formula only works if there is no other resistance in the circuit ( like the 20 ohms of internal resistance ) ... Since the whole of the line would actually have a P.D. of 12 V so AB/AC into 12... This example is actually somewhere on the site's revision pages. The last one in the D.C. area right here: http://www.xtremepapers.com/revision/a-level/physics/dc_circuits.php

Check my previous reply if you need more details. : )

ok you think but you are not sure. i can memorize the situation just like in the questions above. Thank You.

 

[ultraviolet]

Oct/Nov 2011/23 As level
Q1/ d
Q4/ (iv)
Help please :|

 

[confused123]

Oct/Nov 2011/23 As level
Q1/ d
Q4/ (iv)
Help please :|

attach the link to the past paper plz.

 

[ultraviolet]

attach the link to the past paper plz.

I cant find the link for oct/nov 2011 p2 on the site

 

[confused123]

I cant find the link for oct/nov 2011 p2 on the site

then its unlikely that someone will be able to answer. you better write the question here..

 

[confused123]

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s11_qp_21.pdf
help required in 4 b ii part. and 7 b part. Thanks.

 

[CaptainDanger]

A? maybe experimental error which caused wrong mass to be calculate which resulted in difference in densities? caz atoms atoms per unit volume will remain same..share the correct option

I don't know the correct answer... It is C in one of the past year papers... But a few words have been added to this question which has changed it I think...

 

[Scafalon40]

Do you want to know how to solve it or u were just confirming if its a resistance wire?

Confirming.
Again, thank you.

 

[Hussnain]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s05_qp_4.pdf
2(b)(ii).
3(b)(ii)
4(c)(i)
6(b)
7(a),(b) Please answer my questions

 

[anonymous123]

hi bro,
from where did u took this question ? is this answer really correct. i learned the formula in the cambrdige book which says in this case => AB/ AC into Eo i.e .65/1 into 12 = 7.8 Volt.

but here i see a different situation where first we divided ab length with total length and then multiplied with the total resistance of the wire. this gave us resistance across AB wire,

then we used this resistance to find the unknown e.m.f. of the test cell is this whole formula correct in the image?

in the revision section go to dc circuits its the last problem there..

 

[anonymous123]

It is called the "Potential Difference across the resistor ". So if 1 end of the resistor has a potential of 3 V and the potential difference is 6.75, then:
3-x= 6.75
x= 3 - 6.75

Concerning the potential divider question:

I'm not entirely sure of this answer but I understand that since the galvanometer is indicating a zero current, therefore the potential difference between the positive plate and B is zero ( same with the negative plate and A ). Why? Because if there was a potential difference there should be a current passing. This does mean that the potential difference across AB is equal to the potential difference across the cell being tested. Thus, you simply need to find the P.D. across AB.

By using ratio of length to resistance, we get the resistance of AB. Then again by using ratio of resistance to P.D. we get the P.D. across AB.

1 ---> 60
0.65 ---> ?

Then

60 + 20 ---> 12
39 ---> ?

Hope this helped. : )

Jazakallah tht helped!!

just one thing why did u add 60+20?

 

[CaptainDanger]

A? maybe experimental error which caused wrong mass to be calculate which resulted in difference in densities? caz atoms atoms per unit volume will remain same..share the correct option

Yes it is A...

 

[Idolfanatic95]

Aoa, Is there any possibility that i might get solved paper 1 of physics in here? year 2002-09. . .There're so many mcqs im confused about :/

 

[DragonCub]

Yes it is A...

But I think A and C are both correct.
The density, or total mass per unit volume, is equal to mass per atom × number of atoms per unit volume.
P's density is greater than Q's, so MpNp>MqNq.
And it says Np=Nq, so Mp>Mq.

 

[omg]

http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s07_qp_5.pdf
what is the method of finding when the terminal velocity has reachedd??????????????

 

[DragonCub]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s05_qp_4.pdf
2(b)(ii).
3(b)(ii)
4(c)(i)
6(b)
7(a),(b) Please answer my questions