A2 Physics | Post your doubts here

[omg]

can any1 pls gimme the advantages and disadvantages of AM and FM transmissions?????
pleaseeeeeeeeeeeeeeeeeeeeeeeee

 

[ousamah112]

can any1 pls gimme the advantages and disadvantages of AM and FM transmissions?????
pleaseeeeeeeeeeeeeeeeeeeeeeeee

Disadvantages of AM: Lacks higher frequencies that affect the music quality
The quality of Am reception is poorer thn FM
AM are more subjected to noise and distortion
Advantages of AM: The equipment of AM like transmitters and receivers are comparatively simpler and cheap.
Can be transmitted over larger range.
disadvantages of FM : FM transmitters and receiver are electronically complex.
FM transmitter has shorter ranger (30 KM by line of sight) so greater transmitters are required to broadcast to a large area.
Advantages: Interference does not affect FM transmission.

 

[farrukh]

Please post complete solution

 

[étudiante]

In a laboratory demonstration of the photoelectric effect, a metal plate is given an electric charge and light of various wavelengths is shone on to the surface of the plate in turn. It is found that the plate loses its electric charge when the plate is given a negative charge and when ultraviolet light is shone on to the plate.

Explain why the plate does not lose its charge when

(i) the plate is given a positive charge and illuminated by ultraviolet light,
(ii) the plate is given a negative charge and illuminated by visible light.

(4)​

(i) positive charge will attract back the electrons that want 2 escape (unlike charges) hence no loss of charge
(ii) Visible light has a lower frequency, and hence lesser energy, than UV light... thus it cannot provid the electrons it interacts with enough energy for them to break free and hence there is no discharge

 

[pratikdahal]

(i) positive charge will attract back the electrons that want 2 escape (unlike charges) hence no loss of charge
(ii) Visible light has a lower frequency, and hence lesser energy, than UV light... thus it cannot provid the electrons it interacts with enough energy for them to break free and hence there is no discharge

nice one ..and i got the answer to that question !!!

 

[étudiante]

nice one ..and i got the answer to that question !!!

thanx

 

[omg]

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s11_qp_51.pdf
pls can any1 giv me the diagrams og q1 of these papers!!
PLEASE!
http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w11_qp_51.pdf

 

[steel]

o/n/09/42/ 7
o/n/10/41 / 1
o/n/08/4/ 7
o/n/07/4/ 8
o/n/09 41/ 6
m/j/09/4/ 7
m/j/07/4/ 10 and 5
m/j/08/4/ 9 and 5
This are the following question that i dont knw .
help pls !

 

[hassam]

i cant understand the ms point that for wave enrgy cn be continuosly collected so emission shud occur at all frequencies.....the cnfusion is that in case of photon also energy is being collected as it is converted into thermal enrgy if below threshold.....so wats the difference?

 

[Mustehssun Iqbal]

i cant understand the ms point that for wave enrgy cn be continuosly collected so emission shud occur at all frequencies.....the cnfusion is that in case of photon also energy is being collected as it is converted into thermal enrgy if below threshold.....so wats the difference?

did you check the examiner report?? Which question?? How can emission occur at any frequency?? It occurs at the threshold frequency or above it!
In photoelectric emission energy of radiation is not collected inside an electron, that's the classical wave theory which is proved wrong. Emissions occur when the incident radiation has energy more than the work function of the metal.
When the incident radiation has energy not above the work function of the metal, no emission of photoelectrons occur. Energy is given to the surroundings as heat instead. I guess that's what you're trying to say too!
There's got to be something else! Maybe they're collecting energy somehow and releasing it in a form of radiation and providing that radiation as the incident radiation to the metal surface!

 

[Mustehssun Iqbal]

Anyone knows good links or videos about operational amplifiers??

 

[pratikdahal]

can anyone clear away my confusion in this question?? M/J 2004 question 4 (b) (paper 4)
)

 

[ousamah112]

can anyone clear away my confusion in this question?? M/J 2004 question 4 (b) (paper 4)
View attachment 8001 )

Ep is zero at mean position and max at amplitude. there will be no graph in negative region as energy is scalar. So, the graph will be like we get in full-wave rectification of a.c current.

 

[pratikdahal]

Ep is zero at mean position and max at amplitude. there will be no graph in negative region as energy is scalar. So, the graph will be like we get in full-wave rectification of a.c current.

If 'Ep is max at amplitude' then shouldn't the graph be like cos(x)..?? .. but being above time-axis...!!

 

[ousamah112]

If 'Ep is max at amplitude' then shouldn't the graph be like cos(x)..?? .. but being above time-axis...!!

Yes..the graph of y is actually cos(x) graph. so Ep graph will be just like that without being below time-axis.

 

[SkyPilotage]

Anyone knows good links or videos about operational amplifiers??

http://www.youtube.com/results?sear...9.0.1870998.22.22.0.11.11.0.194.1371.4j6.10.0.

Yes..the graph of y is actually cos(x) graph. so Ep graph will be just like that without being below time-axis.

Its like a cosine graph but you flip the negative side on to the positive side. Just like when you connect 4 diodes to obtain full wave recitfication!

 

[Mustehssun Iqbal]

http://www.youtube.com/results?search_query=operational amplifiers&oq=operational amplifiers&aq=f&aqi=g10&aql=&gs_l=youtube-psuggest.3..0l10.1866997.1870849.0.1870998.22.22.0.11.11.0.194.1371.4j6.10.0.

A very good video! thanks loads

 

[hassam]

can anyone clear away my confusion in this question?? M/J 2004 question 4 (b) (paper 4)
View attachment 8001 )

thats wat it shud look like roughly.....
by the way in the last part of this question shudnt the amplitude be smaller also

 

[pratikdahal]

thats wat it shud look like roughly.....
by the way in the last part of this question shudnt the amplitude be smaller also

since the mass is removed..the system oscillates with even more amplitude than before..but this makes the wavelength go small..!!
you can try this question with a thin ruler yourself at home... (it worked for me)

 

[namraahmad]

I need help in the paper Oct/Nov 10 P42 Que 2biii The que values are different and marking scheme values are diff...Really confused???