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Physics: Post your doubts here!

nehaoscar

nehaoscar

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Hey guys, suppose I'm not sure of the answer for a question and I write 2 varied answers for it.
Suppose one of then is correct and the other one is wrong.
Would i get marks for the correct answer or would they not give me any marks since I also have the wrong answer written?
 
The Sarcastic Retard

The Sarcastic Retard

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nehaoscar said:
Hey guys, suppose I'm not sure of the answer for a question and I write 2 varied answers for it.
Suppose one of then is correct and the other one is wrong.
Would i get marks for the correct answer or would they not give me any marks since I also have the wrong answer written?
Click to expand...
They will assume that u were confused and give no marks.
 
A

anasaziz18

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Nowrin Yasmin said:
Walaikumassalam,
For the first question:
compression of ideal gas at a constant temp: the gas if being compressed so work is being done on the gas molecules to bring them closer right? So w is +. Now it is said that temp is constant, but it is obvious that the temp will increase when the gas molecules are brought closer due to more frequent collisions, so to keep the temp constant, we have to cool it down i.e. we're removing thermal energy so q is -. Now, acc to the law of thermodynamic, (-)+(+) = 0. Thus, U is 0.

the heating of a solid with no expansion: When you're heating the solid, obviously you're supplying it with thermal energy so q is +. But it is said that it's done with no expansion i.e. no work is done on the solid particles, so w is 0. Overall, internal energy is increasing due to the particles vibrating faster due to greater thermal energy thus U is +.

the melting of ice at 0 degree C to give water at 0 degree C: for melting, the hydrogen bonds between ice has to be broken thus thermal energy is supplied to do so thus q is +. Now, no work is done in compressing the water molecules of ice. Thus w is 0. Overall, U is +.
Click to expand...



Jazak illahu khairan.
 
A

anasaziz18

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amal sharkawi said:
View attachment 52907
Can anyone answer the question plz
Click to expand...

I got the ans A. The reason is first calculate the total resistances of 3 and 6 ohm together and separately for 2 and 2 ohm. So, the total resistance for 3 and 6 comes 2 ohms and for the 2 and 2 ohms, the total R is 1 ohm. Due to this, the pd across 2 ohms ( 3 ohm and 6 ohm) will be double of that across 1 ohm (2 and 2 ohm). So, we now know that V1=2V2. As a result, V1>V2. Now just consider that the total current flowing is I, so the current flowing thru the 3 ohm resistor can be written as V1/3 and the current flowing thru the 2 ohm can be written as V2/2.
Therefore,
I1=V1/3= 2V2/3
I2= V2/2.
So, 2V2/3 is obviously greater than V2/2. Hence, I1>I2.
 
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Sam Ivashkov

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Hello. I have a question in paper 9702/42/M/J/10, the very last question [12b (ii)]. Can someone explain the working and concept and reasoning behind it step by step? If you do, please show you answer at each step also. Thanks.
 
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