Biology; Chemistry; Physics: Post your doubts here!

[smart_boy]

Thank you so much for your help,im really sorry that there is a lot of question.I really really appreciate your help ur a nice person

I dont know much about o level books but there's this book called IGCSE Biology Coursebook Second Edition by Mary Jones and Geoff Jones. It covers the entire O level syllabus. All of the concepts u hav posted here as doubts - the book can explain beautifully to you... If u find biology difficult just see if u can get hold of it... It would be more practical and quick for you to study from it rather than wait for someone to answer such a long list...

 

[smart_boy]

Thanks.. That site explained well.. Next i need to ask what is the difference between 'dendrons' and 'dendrites' in the human nervous system..??? And out of sensory and motor neurones, which has which and why..??? Pls help me out...

Please help me out with some more doubts..!! I am uploading the two pics of the questions.. Pls let me know as soon as possible because exams aren't far..!! (btw the incomplete word in one of the pics is 'germination')

 

[somya]

Please help me out with some more doubts..!! I am uploading the two pics of the questions.. Pls let me know as soon as possible because exams aren't far..!! (btw the incomplete word in one of the pics is 'germination')

A in both the pics!!

 

[Enferno]

Potassium sulphate is water-soluble so u can use acid-base titration for making it... ur reactants will be potassium hydroxide and sulphuric acid...
The other method cant be used as most potassium compounds are soluble in water... I hope u get it now...

Ok I get it thanks a lot

 

[Miss_Z]

Hi guys! I am new here and need some help with my Physics.

Quoting the 5054 syllabus:
"Candidates should be able to...
...
(d) describe the use of a bistable circuit.
(e) discuss the fact that bistable circuits exhibit the property of memory.
(f) describe the use of an astable circuit (pulse generator).
(g) describe how the frequency of an astable circuit is related to the values of the resistive and capacitative
components."


I am aware that this is is not a compulsory part, but I want to take no risks at all. Can anyone explain as simply as possible what astable and bistable circuits are? I'd be utterly grateful if I could get an explanation for each of the above parts (a,b,c, and d).


Thanks,

Miss_Z

 

[Ltzewei]

Hello everyone! Can you guys explain this to me?

(c) Between points A and B on Fig. 4.1, the temperature is constant as the substance changes
from liquid to solid.
(i) Explain why the temperature stays constant, even though thermal energy is lost by the
substance.
Thanks

 

[Miss_Z]

Hello everyone! Can you guys explain this to me?

(c) Between points A and B on Fig. 4.1, the temperature is constant as the substance changes
from liquid to solid.
(i) Explain why the temperature stays constant, even though thermal energy is lost by the
substance.
Thanks

Assuming you are referring to a typical graph of temperature against time for the solidification of a certain substance,

The heat given out by a liquid during solidification is known as 'latent heat'. Latent heat does not cause a temperature change. The kinetic theory of matter provides an explanation for this.

The kinetic theory explains latent heat of fusion as being the energy released as intermolecular bonds are formed when liquid molecules come together to form a solid. The molecules now take on a more ordered structure as compared to the less ordered structure of the moving liquid molecules. This is why there is no change in temperature during solidification.

Temperature changes only when the substance is cooled in the same state (i.e, when no change of state is involved).


This was a short explanation but I hope it could be of some help to you.

Cheers,

Miss_Z

 

[Mustafa Malik]

Can any 1 provide me wd guess for math 4024 this session???

 

[smart_boy]

A in both the pics!!

Can you kindly explain to me..??

 

[somya]

Can you kindly explain to me..??

first- energy from the sun is taken in by the plants, which have the largest mass!
second- its the cotyledon, which stores food, sooo....
hope you understand!

 

[smart_boy]

first- energy from the sun is taken in by the plants, which have the largest mass!
second- its the cotyledon, which stores food, sooo....
hope you understand!

Ohh... I get it.. Thanks..!!

 

[somya]

Ohh... I get it.. Thanks..!!

you're welcome...!

 

[evilduel]

can some one ans these.. help is really appreciated..
Q: HOW YOU MIGHT CHECK THAT YOU HAVE MADE GOOD ELECTRICAL CONNECTIONS?
Q: GIVE A REASON FOR MAKING THE LENGTH OF EACH NORMAL AT LEAST 6CM?
Q: WHAT ADVANTAGE IS THERE IN USING TRACING PAPER FOR THE SCREEN?
Q: WHY THE EYE NOT PLACED TOO CLOSE TO THE END OF THE RULE?
Q: WHAT WOULD BE THE EFFECT ON THE IMAGE IF THE CENTRE OF THE OBJECT AND THE CENTRE OF THE LENS ARE NOT AT THE SAME HEIGHT?

 

[Nerdz]

Can someone please answer this physics question? I have Physics paper 2 tommorow!
A wave in the electromagnetic spectrum has a wavelength longer than microwaves. explain why the frequency of this wave is lower than the frequency of microwaves? ( Oct/Nov 2002 paper 2, question 3 a)ii )

 

[Ahmad Faizan]

http://www.xtremepapers.com/papers/...nal O Level/Physics (5054)/5054_w11_qp_21.pdf​

​

can you plz look into question 11 part b (2) and part c .. the question is wrong or the answer in marking scheme is wrong ...​

 

[Ahmad Faizan]

Can someone please answer this physics question? I have Physics paper 2 tommorow!
A wave in the electromagnetic spectrum has a wavelength longer than microwaves. explain why the frequency of this wave is lower than the frequency of microwaves? ( Oct/Nov 2002 paper 2, question 3 a)ii )

V = Frequency * wavelength .. as speed of electromagnet wave is same so is frequency inversely proportional to wavelength ... so longer wavelength means lower frequency ........ i hope this helped ...

 

[Nerdz]

V = Frequency multiply wavelength .. as speed of electromagnet wave is same so is frequency inversely proportional to wavelength ... so longer wavelength means lower frequency ........ i hope this helped ...

OMG! Thank you! thank you!

 

[Nerdz]

Physics (5054) Oct? Nov Paper 2 2002 Question 4 part c? Thanks

 

[Ahmad Faizan]

Physics (5054) Oct? Nov Paper 2 2002 Question 4 part c? Thanks

anytym... now in Q 4 part c .. u have to find the total kWh of all appliance (1*2 + 2*0.1+ 0.6*1.5 + 3*0.4 + 1.5*2 = 7.3 kWh ) now add this to previous reading (6350.5 + 7.3 = 6357.8 kWh) which is the reading at end of day ......

 

[Nerdz]

anytym... now in Q 4 part c .. u have to find the total kWh of all appliance (1*2 + 2*0.1+ 0.6*1.5 + 3*0.4 + 1.5*2 = 7.3 kWh ) now add this to previous reading (6350.5 + 7.3 = 6357.8 kWh) which is the reading at end of day ......

Thank you very much!