Question

If $\Delta Q$ and $\Delta W$ represents the heat supplied to the system and the work done on the system respectively, then the first law of thermodynamics can be written as

• A. $\Delta Q=\Delta U+\Delta W$
• B. $\Delta Q=\Delta U-\Delta W$
• C. $\Delta Q=\Delta W-\Delta U$
• D. $\Delta Q=-\Delta W-\Delta U$

Answer 1

The correct option is B $\Delta Q=\Delta U-\Delta W$

from FLOT $\Delta Q=\Delta U+\Delta W$
$\because$ Heat supplied to the system so $\Delta Q\to Positive$ and work is
done on the system so $\Delta W\to Negative$
Hence $+\Delta Q=\Delta U-\Delta W$