Discussion Forum



1)

An ideal gas in a cylinder is compressed adiabatically to one -third of its original volume. A work of 45 J is done on the gas by the process. The change in internal energy of the gas and the heat flowed into the gas, respectively are


A) 45 J and zero

B) -45 J and zero

C) 45 J and heat flows out the gas

D) -45 J and heat flows into the gas

Answer:

Option A

Explanation:

For adiabatic process, $\triangle Q$=0

Now, from first law of thermodynamics , we have

 $\triangle Q= \triangle U+ \triangle W$

 $\triangle W=$ -45 J  or work done on the gas

 $\Rightarrow$    $ 0= \triangle U-45$

 $\Rightarrow$    $\triangle U= 45 J$