Biology; Chemistry; Physics: Post your doubts here!

[Saad Mughal]

can any1 plz answer this question! this is from a physics past ppr in Oct 10!

Explain, in outline, how a low-density cloud of hydrogen in space becomes a star.

Various clouds get together forming a big blob with a lot of gravitational potential energy, these large blobs of cloud pull towards them other particles and clouds as well (due to gravity), at some time, the potential energy changes into heat energy and fusion occurs where hydrogen atoms combine to form helium atoms. This, very large blob shines brightly because of the great amount of energy produced by fusion and hence, becomes a huge star in the galaxy.
This is not a thorough explanation but should be enough for the answer.

 

[Mohammad Farzanullah]

Various clouds get together forming a big blob with a lot of gravitational potential energy, these large blobs of cloud pull towards them other particles and clouds as well (due to gravity), at some time, the potential energy changes into heat energy and fusion occurs where hydrogen atoms combine to form helium atoms. This, very large blob shines brightly because of the great amount of energy produced by fusion and hence, becomes a huge star in the galaxy.
This is not a thorough explanation but should be enough for the answer.

thanks for free service!
aap ka world top aye!

 

[Saad Mughal]

thanks for free service!
aap ka world top aye!

Insha ALLAH, ALLAH (SWT) aapki zubaan mubarak karyn!

 

[Amnaa]

please help me in Phy... i have done 2 Mcqs paper and got 31 , 30..

 

[Amnaa]

kya kisi ke pas Phy ke notes hain.. covering all the topics.?? please share with me

 

[Saad Mughal]

kya kisi ke pas Phy ke notes hain.. covering all the topics.?? please share with me

These are good,
http://newurlsothatthedumbpeopledontgetfreenotes.files.wordpress.com/2012/03/physics-igcse.pdf

 

[Amnaa]

These are good,
http://newurlsothatthedumbpeopledontgetfreenotes.files.wordpress.com/2012/03/physics-igcse.pdf

Thank you sooo muchh!! these are reallllyyy Good!!!

 

[Mustafa Malik]

so what abt this yr? Can it go lower , i mean for A*??? IS ur source reliable?

 

[HarithAslam]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s09_qp_1.pdf
why is Q30 B and not A?

 

[asma tareen]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s09_qp_1.pdf
why is Q30 B and not A?

beacause oth live and earthing wires are attached together

 

[Mustafa Malik]

i have a question : if a gas sealed in a container is heated , will the average distance bw molecules increase? I have a topical n it says no cuz there is no change in its state so.... though i think distance shud increase?

 

[Osaid Zahid]

Can Some one also answer this ..... We know that there in A/C circuitry there is live and neutral Wires in a switch board ... But have you noticed that when we plug in those two pin appliances you can really place then any way around...Doesn't Live and neural matter here .... There might be a rectification bridge if the appliance is DC... but what about those bulbs that work completely on AC supply. and why why electromagnetic waves are easily absorbed when their wavelengths are short and they are at high frequencies.....like Gamma rays ... they are dangerous while radio waves can easily pass through atmosphere without being absorbed too much...
also when Beta rays emits from a radioactive from a source the neutron splits electron files away and +ve charge is left behind how is that charge neutralized.

One last thing when a current flows through a How does a circular magnetic field at 90 deg just from around moving electrons...​

 

[farhan141]

Can Some one also answer this ..... We know that there in A/C circuitry there is live and neutral Wires in a switch board ... But have you noticed that when we plug in those two pin appliances you can really place then any way around...Doesn't Live and neural matter here .... There might be a rectification bridge if the appliance is DC... but what about those bulbs that work completely on AC supply. and why why electromagnetic waves are easily absorbed when their wavelengths are short and they are at high frequencies.....like Gamma rays ... they are dangerous while radio waves can easily pass through atmosphere without being absorbed too much...
also when Beta rays emits from a radioactive from a source the neutron splits electron files away and +ve charge is left behind how is that charge neutralized.

One last thing when a current flows through a How does a circular magnetic field at 90 deg just from around moving electrons...​

Wait for Saad Mughal to get on this . I'm too tired to read all this now

 

[iamLbert]

Various clouds get together forming a big blob with a lot of gravitational potential energy, these large blobs of cloud pull towards them other particles and clouds as well (due to gravity), at some time, the potential energy changes into heat energy and fusion occurs where hydrogen atoms combine to form helium atoms. This, very large blob shines brightly because of the great amount of energy produced by fusion and hence, becomes a huge star in the galaxy.
This is not a thorough explanation but should be enough for the answer.

i dun get ur idea, what is blobs?

 

[HarithAslam]

beacause oth live and earthing wires are attached together

so a large current should flow through the earth wire, blowing the fuse in the plug.

 

[asma tareen]

well voltage is highest in the live wire while in neutral and earth wire the voltage have zero voltage but now as the earth wire would be connected with live wire si voltage would aLso flow through the earthing wire which would make the circuit live and the person can get a shock .
simply transferring of voltage to the earth wire wont let it perform its function i guess

so a large current should flow through the earth wire, blowing the fuse in the plug.

 

[Amnaa]

ca any one expain me how velocity become negative?

 

[iamLbert]

moved in opposite direction ( move backwards )

ca any one expain me how velocity become negative?

 

[iamLbert]

May I ask how to answer 9 (a) and (b) below :

Source : OL 5054/02/M/J/09​

​

Thanks for your attention and help ​

 

[TheStallion-Reborn]

Various clouds get together forming a big blob with a lot of gravitational potential energy, these large blobs of cloud pull towards them other particles and clouds as well (due to gravity), at some time, the potential energy changes into heat energy and fusion occurs where hydrogen atoms combine to form helium atoms. This, very large blob shines brightly because of the great amount of energy produced by fusion and hence, becomes a huge star in the galaxy.
This is not a thorough explanation but should be enough for the answer.

is this in our syllabus??