Biology; Chemistry; Physics: Post your doubts here!

[Iridescent]

for A levels and even universities consider your grades.

 

[SalmanPakRocks]

Plz stay on topic everyone

 

[Saad12345]

the green FEDERAL book by prescott is really good for chemistry....chemistry matter's good too.
and for physics,i'd suggest ''explaining physics'' by stephen pople

ALright thanks

 

[DANGERBP]

i want a biology a level notes that contain mostly everything plzzzzz ide b gratefull =)

 

[haha101]

Does any one have Imaran merchants notes ? I really need them plx ! And sir Yawars notes

 

[Duanoor]

Can anyone tell me what is interference in Physics?

interference occurs when two waves fall in the same medium..there are two types of interference :constructive interference and distructive...constructive occurs when crest falls on crest or trough falls on trough...distructive occurs when crest falls on trough.....we can observe interference by young's double slit experiment...

 

[Duanoor]

Nopes, the place u are talking abt between Al and Zn thats for Carbon which is just written there for understanding H original and correct position is above Cu !
Remember how Fe is reduced by carbon and not by hydrogen
Still confused look at a detailed Reactivity series on GOOGLE !

agreed!

 

[legion]

ummm last question, last part??? :O
explanation too?
n11 chemistry p42???
cant upload it so here's the link.
http://www.mediafire.com/?d5lwx8xvc8lcs8z

 

[khanrocks20]

please.... need help for bio atp reply asap

 

[daredevil]

guys can someone please explain to me what a npn transistor and a capacitor is? what is a bistable circuit and its use? and what is an astable circuit?
we have finished the syllabus but we havent done it, teachers say that it doesnt come often and so they dont teach it, but just to be on the safe side, can somebody please explain to me these? thank you!

heyy is this transistor, astable and bisatable stuff in o levels physics? i know capacitor is but never read this other stuff.... plz tel me its not in our course!! >__<


Also can anyone explain the advanced electronics section of physics o levels course and half life of radioactive substances too.... bcuz we did it in a jiff at school and i don't get it still. help me!!

 

[daredevil]

Q.1 what is the purpose of a ratchet?
Q. 2 why is there a 20*C mark on the measuring cylinder? (i read this question in some notes and i don't even if there is a mark so obv i didn't know the answer to this question.)

 

[Tharindu]

heyy is this transistor, astable and bisatable stuff in o levels physics? i know capacitor is but never read this other stuff.... plz tel me its not in our course!! >__<


Also can anyone explain the advanced electronics section of physics o levels course and half life of radioactive substances too.... bcuz we did it in a jiff at school and i don't get it still. help me!!

no its not stated on this years syllabus so they will definitely not ask it....the capapcity is there. A half life of a substance is the time taken for then nuclei to half....like say if the half life of uranium is 2000 years that means that if there are 5000 uranium radiation then in another 2000 years there will be only 2500 radiations...

 

[Tharindu]

Can anyone tell me what are the important things to know about the section metals, air and atmosphere because I havent learnt it at all

 

[daredevil]

no its not stated on this years syllabus so they will definitely not ask it....the capapcity is there. A half life of a substance is the time taken for then nuclei to half....like say if the half life of uranium is 2000 years that means that if there are 5000 uranium radiation then in another 2000 years there will be only 2500 radiations...

oh ok..... thanks!

 

[Duanoor]

please.... need help for bio atp reply asap

wht's ur question?

 

[scouserlfc]

Q.1 what is the purpose of a ratchet?
Q. 2 why is there a 20*C mark on the measuring cylinder? (i read this question in some notes and i don't even if there is a mark so obv i didn't know the answer to this question.)

Remember the micrometer screw gauge,the ratchet serves a purpose of not applying too much pressure on the substance whose diameter is required so an accurate reading can be taken !

2.this 25 degrees celsius mean that the cylinder works best in this temperature stated and it was calliberated in this temperature so it shud be used in this temp. if its not used then due to expansions the value may be low or high and not accurate

 

[mintchocolate4567]

Christmas lights are connected in series....a set of 20 bulbs are connected in series this way.a voltage of 240 V is supplied to the bulbs....why is it wrong to connect a 40 bulb set in this circuit?

 

[mintchocolate4567]

Why is it wrong to use:
A) a 3 A fuse in the plug of an electric fan using 10 A,
B) a 13 A fuse in the plug of a radio using 1.5 A?

 

[smzimran]

Why is it wrong to use:
A) a 3 A fuse in the plug of an electric fan using 10 A,
B) a 13 A fuse in the plug of a radio using 1.5 A?

a) Because the fuse will blow at 10 A and the fan will never work. (fuse rating too low)
b) Because the fuse will never blow even if current exceeds 1.5 A. (fuse rating too high)

 

[smzimran]

Christmas lights are connected in series....a set of 20 bulbs are connected in series this way.a voltage of 240 V is supplied to the bulbs....why is it wrong to connect a 40 bulb set in this circuit?

Each bulb will not get the sufficient voltage to light up brightly and so they will become dim. That is why.