Answer:
660KJ
Explanation:
Given
Let Q = Heat Loss from room = 50kj/min
Let W = Work Supplied to room = 1.2KW
1 kilowatt = 1 kilojoules per second
So, W = 1.2KJ/s
In heat and work (Sign Convention)
We know that
1. Heat takes positive sign when it is added to the system
2. Heat takes negative sign when it is removed from the system.
3. Work done is considered positive when work is done by the system
4. Work done is considered negative when work is done on the system.
From the above illustration, heat loss (Q) = -50KJ/Min
In 30 minutes time, Q = -50Kj/Min * 30 Min
Work done in 30 minutes = -1500 KJ
Also, work supplied = -1.2Kj/s
Work supplied to the system in 30 minutes = -1.2Kj/s * 30 minutes
W = -1.2 KJ/s * 30 * 60 seconds
W = -2160KJ
In thermodynamics (First Law)
Q = W + ΔU
-1500 = -2160 + ΔU
∆U = 2160 - 1500
∆U = 660KJ
