Question

In a closed insulated container a liquid is stirred with a paddle to increase the temperature, which of the following is true?

• A. $\Delta E=W\ne 0,q=0$
• B. $\Delta E=W=q\ne 0$
• C. $\Delta E=0,W=q\ne 0$
• D. $W=0,\Delta E=q\ne 0$

Answer 1

The correct option is A $\Delta E=W\ne 0,q=0$

The mathematical form of first law of thermodynamics: $q=\Delta E+W$
Since the system is closed and insulated, $q=0$
Paddle work is done on system. $\therefore W\ne 0.$
Temperature and hence internal energy of the system increases. $\therefore E\ne 0$.