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Physics: Post your doubts here!

msohailz14

msohailz14

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A star said:
yes but the change in internal energy of a system= work done on/by a gas + change in thermal energy of the system
in the freezing part the temprature is constant but there is work done on the gas by the atmosphere cause it contracts. or is the oposite cause of abnormal behaviour of water?
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Your doubt is valid, but you have made me confused as well. I'll have to check with someone else on this one. Nice thought.
 
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hela

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In communication systems,which of the uplink or downlink will swamp which because in the book says the opposite
 
Champ101

Champ101

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Monojit Saha said:
(iii) is really weird i get 746.
They already mentioned the volume of gas but they found it again. Dont get them. :p
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We have to calculate the volume again, because there is a change in pressure when we put the balloons in the cylinder. So we use Boyle's law as the temperature remains constant.
Now this new volume is volume of the cylinder. It's the total of the balloons and the hydrogen volume in the cylinder. Read the question again try to visualize this, you will definitely get it! ;)
 
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boxfire1995

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Menu Mendz said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_qp_4.pdf
Q10 LAST PART, SOMEONE PLEASEEEEEEEEEEE!
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Since the frequency of carrier wave is 50khz, that means the time period will be 20micro seconds. That means the small wave will be of 20micro seconds. Bandwith is 2 times the frequency of the information signal. So half of bandwith is 5khz which represents a time period of 200micro-herts. THAt meansin 200 microseconds, the amplitude changes from the highest to the next highest or vice versa. Im sure ive given you enough data to make the graph
 
Champ101

Champ101

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thats_me said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s08_qp_4.pdf 11a ii
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Its a frequency modulation, so there wont be any change in amplitude, just the frequency is affected.
Now, the carrier wave is modulated using the signal wave. The frequency shift produced by the signal is = 1.5 * 20 =30 KHz. So the limits of frequecy would be:
(500+30) and (500-30) which is 530 KHz and 470 KHz. And this variation is frequecy occurs 8000 times every second.
 
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boxfire1995

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Menu Mendz said:
can u draw a diagram and explain it to me please??????????
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I can draw it but i dont know how to upload the picture. Its going to be an amplitude modulated wave with the peak point at around hundred and the carrier waves time period will be 20microseconds.
 
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