Question

A system is provided with $200cal$ of heat and the work done by the system on the surrounding is $40J$. the internal energy

• A. Increases by 600 J
• B. Decreases by 800 J
• C. Increase by 800 J
• D. Increases by 160 J

Answer 1

Correct option: (C)
From first law of thermodynamic,

$△U=q+W$

$△U=\text{Change in internal energy}$

$q=\text{Heat supplied}$

$W=\text{Work done}$

$q=200cal=200\times 4.2=840J$
$W=-40J$
$△U=q+w=840-40=800J$

Hence, the correct option is (C).