P1 CIE physics doubts

[Saladin]

can sum1 please give me the paper, maybe i can help.

[~ A.F ~]

R= pl/A

it says both wires have the exact volume..i.e the exact area and length x

These are the only factors on which the resistance depends on..

and so both have equal resistances

[sweetie]

here is the paper
thanx A.F

[Saladin]

I hate to disagree with you A.F, but even though the markscheme says C, I am not entirely convinced that that is the answer. I think we need astar to explain.

[~ A.F ~]

Here's ur explanation guys:

Resistance of P= pl/A...agree?

Resistance of Q:

Area of each wire of the seveen wires= A/7...right?

now R=pl/A= pl/(A/7)= 7pl/A...so far so good..thats the are for each wire..

now total area of resistor Q:

R_T = (1/R₁ + 1/R₂ ....)^-1

=(1/(7pl/A) x7)^-1 = pl/A

hope that's clear now

[nid404]

Thanks A.F + rep

[astarmathsandphysics]

I think I remember the question. Use 1/r=1/100+6x1/100/ on a phone now

[~ A.F ~]

Thanks Nid

[Saladin]

I remember this question too, and I could answer it myself, but this is the problem, I dont think that would practically happen. Does this thing practically happen sir??

Its kinds hard for me to take in also.

I got it like this, reducing the diameter will reduce resistance, but since the wires are in paralell, that will even out. What I have a hard time swallowing is if this would really happen.

[sweetie]

Here's ur explanation guys:

Resistance of P= pl/A...agree?

Resistance of Q:

Area of each wire of the seveen wires= A/7...right?

now R=pl/A= pl/(A/7)= 7pl/A...so far so good..thats the are for each wire..

now total area of resistor Q:

R_T = (1/R₁ + 1/R₂ ....)^-1

=(1/(7pl/A) x7)^-1 = pl/A

hope that's clear now

yup, now iam convinced 
thanx A.F

[sweetie]

Q33 plz of the same year may07

[nid404]

still not gotten it?

ok wait...i'll get back in a while

[nid404]

in a parallel circuit voltage remains constant

In the first wire(resistors are in series), the 2 resistors have the same value, so voltage splits equally...V1= 2/2=1 V  [voltage splits in series]
In the second wire, voltage splits according to ratio of resistance...V=IR (directly proportional) ...so in the 3 ohm resistor it would be 3/5 X2=1.2V  (since total R=5...ratio is 3/5)

V1-V2= 1-1.2= -0.2

[sweetie]

Q10, 22,30 and 40

Thank You

[nid404]

Q 10) acceleration of the blocks is constant
the block has a Force= 4ma
F is directly proportional to m
X uses only 1/4 of the force to acc
3/4 of the force will be applies on Y...for both the blocks to move toether, hence D  (acc is constant)