# What is the change in internal energy?

A paddle wheel is used for stirring a liquid contained in a tank supplied 6000 kJ of work and during the stirring operation the tank lost 1500 kJ of heat to the surroundings.If the tank and liquid are considered as a system what will be its change in internal energy.

Asked on 29th September 2019 in

First law of thermodynamics tells that

$dQ=du+dW$

Therefore

$$-1500=du-6000 \\\Rightarrow du=6000-1500 \\\Rightarrow du=4500\;kJ$$

So change in internal energy of the system is 4500 kJ