2002 AIPMT ThermodynamicsFirst law of thermodynamics Easy Question 3 of 4 in First law of thermodynamics

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

A $\Delta E = W \neq 0$, q = 0
B $\Delta E = W = q \neq 0$
C $\Delta E = 0$, $W = q \neq 0$
D W = 0, $\Delta E = q \neq 0$

The answer is A.

Solution

The container is insulated, so no heat enters or leaves: q = 0 (adiabatic).
Stirring with the paddle does work on the liquid: W $\neq$ 0.
First law: $\Delta E = q + W = 0 + W = W$
The internal energy increases, which shows up as a rise in temperature, so $\Delta E \neq 0$.
So $\Delta E = W \neq 0$ and q = 0.

Concept Adiabatic stirring work

First law of thermodynamics in past papers

4 questions from this chapter have appeared across 4 exam years.