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[ Official ] How was the Prelims 2021 paper?

How was the paper guys ? 

jack_Sparrow,curious_kidand28 otherslike this
1.7m views

4.8k comments

assistantsaid

@Guesswhoshere whistle weight is part of lid ,isn't it .it comes attached


both types of pressure cookers are there. But i guess the common standard ones do have removable whistle weights. 




Jesse_pinkman,
5.9k views
@Guesswhoshere buddy that way  every part can be mantled or dismantled...


5.8k views

Pam123said

Just a doubt regarding the pressure cooker q, why are all keys saying that temperature of the flame doesn’t matter. So does it, doesn’t?

It doesn't. It's basic thermodynamics. If you have a science background, read the rest

A pressure cooker is an example of a closed system

For closed systems, ideal gas equation is PV = nRT (Pressure*Volume = a constant(nR)*Temperature)

Volume, nR are constant

Hence Pressure and Temperature are directly proportional

A pressure cooker is designed to operate at a maximum pressure - which depends on the strength of the material etc. 

The temperature at which cooking happens will depend on that pressure only





Pam123,sleeplessnights89
4.8k views
@oopsie okay it seems like a plausible explanation to me. That settles the answer to 1 & 3. But 3 is being questioned as well by people. But thank you for the explanation.


4.7k views
@Pam123 yes, seems UPSC made a typing mistake.
But higher the weight of the lid, higher will be the downward pressure it can exert and hence higher the maximum pressure at which the cooker can operate. This is a probable explanation. Not sure
4.6k views
Guys when the entire Meaning of the 3rd statement is changed, even 1&3 seems to be wrong. 1 only should be the answer which isn’t given. According to me, there are high chances for pressure cooker question to be deleted. 


5.2k views

With respect to the Pressure cooker question:

At constant volume increasing pressure increases temperature. However, to increase the pressure there has to be some source so as to fulfill the law of conservation of energy. Pressure cannot increase on its own.

5.2k views
@oopsie so if there are 2 identical pressure cooker cooking same quantity of food, one is cooked at lower flame and other is cooked at the highest flame of the burner both will get cooked at the same time because flame temperature doesn't plays a role..... 


shaanu4595684,
5.2k views

5HTsaid

With respect to the Pressure cooker question:

At constant volume increasing pressure increases temperature. However, to increase the pressure there has to be some source so as to fulfill the law of conservation of energy. Pressure cannot increase on its own.

heat and temperature are two different things. 

It's similar to wind and pressure gradient in geography. Wind will blow from higher pressure to lower pressure

Similarly heat will flow from higher temperature to lower temperature

As long as the temperature of the flame is any value higher than the temperature of the cooker, the flame can heat the cooker

4.3k views
Pardon for the sarcastic language, but if flame temperature doesn't plays a role in cooking temperature then instead of gas burners that are used in our houses we can cook food on candle? 
Dionysus,slightedge109and3 otherslike this
5.1k views
@drlokeshyadav761665 read above. I've explained it. Hope this settles it


4.3k views
@drlokeshyadav761665 both will get cooked at same temperature (which has been asked by UPSC), however, their cooking time may vary (which has not been asked by UPSC)......understand the cooker question of special case of boiling water.....water always boils at 100 celsius at mean sea level in an open vessel....irrespective of temperature of flame...if you boil more water...it will take more time to boil,.....but will boil at 100 celsius only.....in case of cooker same principle applies but by artificially increasing the pressure inside cooker the same water now boils at may be 120 or 130 celsius.


5k views
@drlokeshyadav761665 you can technically use a candle too. But the amount of heat energy generated by the candle is much lesser than what your stove can. Will take a lot of time and lot of candles to cook the food :P


sleeplessnights89,
4.2k views
@drlokeshyadav761665 flame temperature of single candle and flame temperature produced by lighting 100 candles will be same...if you want to cook food in cooker using candles try cooking by lighting 100 candles...i guess...the cooker would surely whistle


5k views
Professor ngl राजा बाबू 🥳🌈 on Twitter: "… "
MikeWozniak,Ayushi7and15 otherslike this
4k views

srivalliguru940said

Guys when the entire Meaning of the 3rd statement is changed, even 1&3 seems to be wrong. 1 only should be the answer which isn’t given. According to me, there are high chances for pressure cooker question to be deleted. 


Questions dnt get deleted like this. Upsc will never accept it's mistake. They will just come up with an ans which can be anything between 1 and 2,1 and 3,1 2 and 3. They anyways release ans key after final result and by that time none of the arguments we are making will matter. Every year some questions are controversial(for aspirants and not for upsc) but such questions never get deleted. Only Outright blunders like translating civil disobedience movement as non coop mvmt, as was done in 2020 ,have chance of getting deleted. If there's even 1% scope of question being correct,upsc will not delete it.

One can go to the court(like 2017) but thn upsc has its own way of handling things and it will win(like 2017).

Master,
4.9k views
yeah that’s true. But I hope, they cancel the question due to two reasons : 
1. the word “ maximum” is missing in the question. The maximum temperature doesn’t depend on temp of the flame ( it’s given in UPPCS 1995 prelims which is being quoted by few people ). 
2. Upsc didn’t even copy the question from
that guide correctly. It’s given as weight on the lid in both uppcs as well as that question bank. 

So there is a mistake in the question as well as the options. So let’s hope it gets deleted. The worst possible thing is, they ignore the concept as well as generalist approach and just give the answer as 1&2. But that’s meaningless. So let’s see. 

All the best 


4.5k views

oopsiesaid

Pam123said

Just a doubt regarding the pressure cooker q, why are all keys saying that temperature of the flame doesn’t matter. So does it, doesn’t?

It doesn't. It's basic thermodynamics. If you have a science background, read the rest

A pressure cooker is an example of a closed system

For closed systems, ideal gas equation is PV = nRT (Pressure*Volume = a constant(nR)*Temperature)

Volume, nR are constant

Hence Pressure and Temperature are directly proportional

A pressure cooker is designed to operate at a maximum pressure - which depends on the strength of the material etc. 

The temperature at which cooking happens will depend on that pressure only





But it is not adiabatic either so outside heat will affect the inside of the system


Temp from outside definitely have an effect. 

Jai Shree Ram !


3.4k views

srivalliguru940said

yeah that’s true. But I hope, they cancel the question due to two reasons : 
1. the word “ maximum” is missing in the question. The maximum temperature doesn’t depend on temp of the flame ( it’s given in UPPCS 1995 prelims which is being quoted by few people ). 
2. Upsc didn’t even copy the question from
that guide correctly. It’s given as weight on the lid in both uppcs as well as that question bank. 

So there is a mistake in the question as well as the options. So let’s hope it gets deleted. The worst possible thing is, they ignore the concept as well as generalist approach and just give the answer as 1&2. But that’s meaningless. So let’s see. 

All the best 


UPPCS question does not mark that temperature is wrong.

In that only 2 things was mentioned and no combination fits for temperature one from the options. Does not mean temperature was Wrong. 

Jai Shree Ram !


6.7k views
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