11.Thermodynamics
easy

किसी उष्मागतिक निकाय को आरेख में दिखाये गये अनुसार $ABCD$ चक्र से गुजारा जाता है। इस चक्र में गैस द्वारा निकाली गई ऊष्मा का मान होगा

A

$2PV$ $\;$

B

$\;4{\rm{\;PV}}$

C

$\;{\rm{PV}}$

D

$\;\frac{{PV}}{2}$

(AIPMT-2012)

Solution

In a cyclic process,

$\Delta U = 0$

In a cyclic process work done is equal to the area under the cycle and is positive if the cycle is clockwise and negative if anticlockwiase.

$\therefore \,\,\,\Delta W =  – Area\,of\,rectangle\,ABCD =  – P\left( {2V} \right)$

$ =  – 2PV$

According to first law of thermodynamics

$\Delta Q = \Delta u + \Delta W\,or\,\Delta Q = \Delta W\,\,\left( {As\,\Delta u = 0} \right)$

$i.e.,$ heat supplied to the system is equal to the work done

So heat absorbed,$\Delta Q = \Delta W =  – 2PV$

$\therefore $ Heat rejected by the gas  $ = 2PV$

Standard 11
Physics

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