Physics: Post your doubts here!

[Kirabo Takirambudde]

Hey guys!! This is highly important for Thursday!

What is the function of each of these 3 devices used in a mobile phone handset
-Series to Parallel
-Modulator
-Demodulator

 

[Goku]

Thank you sooooo much for both the questions!! You're so nice!! :')
And I figured out what I was doing wrong in this question I didnt do this step!!
P = 2.5 X 10^5 Pa

So that was the problem there,thanks again and may Allah bless you!!

Goku For Q2(a),
Number of atoms/particles = Number of moles X Avogadro's constant (The old formula we studied in O Levels applies here )
Anyway, we will be applying this formula to find the number of atoms of gas. We have the Avogadro's constant so we only need the number of moles of the gas.
Let's list the data we have.
P = 2.5 X 10^5 Pa
V = 4.5 X 10^3 cm^3 = 4.5 X 10^-3 m^3.
R = (value from data given in booklet) = 8.31 J/ K mol
T = 290 K
Put this into the Ideal gas equation PV = nRT and hence you get the value of n. Place this value of n into this equation Number of atoms/particles = Number of moles X Avogadro's constant and hence you get the answer.

 

[Wanzi21]

9702_w06_qp_4.pdf

eplain pls for question 2?

 

[geek101]

october/november 2005 p1 no 18
pls explain.......

ok, the formula for pressure = density (rho) x g x h
they want us to find the depths at which both the liquids will have the same pressure acting on them.
the g = 9.81 ms^-2 for both
d for X >> 800 kgm^-3
d for Y >> 1200 kgm^-3

now for each option multiply the d, g and h to get the pressure
for A: x >> 8 x 9.81 x 800 = 62 784 and y >> 12 x 9.81 x 1200 = 141 264 ...they are not similar so eliminate A.
for B: x >> 10 x 9.81 x 800 = 78 480 and y >> 10 x 9.81 x 1200 = 117 720 ...they are not similar so eliminate B.
for C: x >> 15 x 9.81 x 800 = 117 720 and y >> 10 x 9.81 x 1200 = 117 720 ...they match! so C!

 

[Alice123]

ok, the formula for pressure = density (rho) x g x h
they want us to find the depths at which both the liquids will have the same pressure acting on them.
the g = 9.81 ms^-2 for both
d for X >> 800 kgm^-3
d for Y >> 1200 kgm^-3

now for each option multiply the d, g and h to get the pressure
for A: x >> 8 x 9.81 x 800 = 62 784 and y >> 12 x 9.81 x 1200 = 141 264 ...they are not similar so eliminate A.
for B: x >> 10 x 9.81 x 800 = 78 480 and y >> 10 x 9.81 x 1200 = 117 720 ...they are not similar so eliminate B.
for C: x >> 15 x 9.81 x 800 = 117 720 and y >> 10 x 9.81 x 1200 = 117 720 ...they match! so C!

thanks

 

[BettyBoop]

help?

 

[geek101]

BettyBoop here, use the equation s = ut + 0.5 at ^2 and because the ball is dropped from rest >> u = o ms^-1
so s = 0.5 a t^2
rearrange and make a the subject of the formula >> a = 2s / t^2
now s = h
and t will be the difference in the squares of t1 and t2
so a = 2h / ( t1^2 - t2^2 )

 

[Mattman]

May June 2004 question 6 paper 4 please..TT

 

[InnocentAngel]

Please help me friends : In the syllabus it says as such for the chapter communicating info. which frequencies n wavelength r they asking for? Can someone please write them down here ? Thanks in advance.

 

[Sandhya Mahat]

Somebody please help me with this question. The answer is 20J but I don't know the process. Please answer along with the process.
50J of heat energy is supplied to a fixed mass of gas in a cylinder. The gas expands, doing 20J of work. Calculate the change in internal energy of the gas.

 

[momo_khan]

View attachment 18334help?

is it D ?

 

[Soldier313]

Aoa wr wb
Can someone please help me with qn no 5 b) of this paper, would really appreciate it
qn paper : http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s10_qp_41.pdf
ms: http://www.xtremepapers.com/papers/...d AS Level/Physics (9702)/9702_s10_ms_41.pdfu

JazakAllah khair. Thank you.

 

[Taci12]

Aoa wr wb
Can someone please help me with qn no 5 b) of this paper, would really appreciate it
qn paper : http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_41.pdf
ms: http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_ms_41.pdfu

JazakAllah khair. Thank you.

(i) Faraday's law :rate of change of flux proportional to induced EMF

Explanation: When the coil is placed such that its plane is perpendicular to the magnetic field, and is kept stationary, the coil will not cut magnetic lines of force. There will be no change in magnetic flux, hence induced EMF is zero.

(ii) Anything that would cause change in flux linkage of coil such using an A.C, moving coil, moving conductor, etc

Hope I helped!

 

[Soldier313]

(i) Faraday's law :rate of change of flux proportional to induced EMF

Explanation: When the coil is placed such that its plane is perpendicular to the magnetic field, and is kept stationary, the coil will not cut magnetic lines of force. There will be no change in magnetic flux, hence induced EMF is zero.

(ii) Anything that would cause change in flux linkage of coil such using an A.C, moving coil, moving conductor, etc

Hope I helped!

Thanx a lotttt sis! God bless you

 

[Sandhya Mahat]

Somebody please help me with this question. The answer is 20J but I don't know the process. Please answer along with the process.
50J of heat energy is supplied to a fixed mass of gas in a cylinder. The gas expands, doing 20J of work. Calculate the change in internal energy of the gas.

 

[Sandhya Mahat]

Half wave rectifier circuit is used to rectify an a.c input voltage of 240 r.m.s. The output resistor has resistance 25kiloohm. Peak value of input voltage is 340V. Estimate the average current in the output resistor.
Somebody help me with this question please.

 

[Taci12]

Thanx a lotttt sis! God bless you

God bless you too brother! All the best for exams

 

[Tasnim Akhter]

help me out.....
10lg(Pm/3.4*10^-19)=24
Pm=??

 

[VelaneDeBeaute]

Somebody please help me with this question. The answer is 20J but I don't know the process. Please answer along with the process.
50J of heat energy is supplied to a fixed mass of gas in a cylinder. The gas expands, doing 20J of work. Calculate the change in internal energy of the gas.

I am not sure if the answer is 20J. I'm going to write down everything I think makes sense.
Change in Internal Energy = Change in Heat Energy + Change in Work done by the system on the gas
= 50J + (-20J) = 30J

 

[Gémeaux]

Somebody please help me with this question. The answer is 20J but I don't know the process. Please answer along with the process.
50J of heat energy is supplied to a fixed mass of gas in a cylinder. The gas expands, doing 20J of work. Calculate the change in internal energy of the gas.

VelanedeBeaute did it correct i guess :/. Its like the 20J work is what *the gas does on the cylinder*, which is why it has to be subtracted.
If according to first law of thermodynamics, work done on gas is to be added, work done *by* the gas on the system is to be subtracted.