Question

When the door of a refrigerator is kept open then the room temperature starts
A. Cool down
B. Hot up
C. First cool down then hot up
D. Neither cool down nor hot up

Answer 1

Hint: This is the question based on thermodynamics. There are two main devices used for heat transfer. They are heat engines and heat pumps. By knowing the working principle of them we can answer the question.

Complete answer:
Heat engine is a device which will take the heat from the hot body reservoir called a source and transfer the heat to the cool body reservoir which acts as a sink and does some work. No device will be hundred percent efficient so heat engines cannot convert the entire heat into work form. So some of the heat is lost to the sink and the rest is converted into work.
The entire mechanism of the heat engine is shown in the diagram below.

Heat pump is a device which will take the heat from the cold body reservoir called that acts as a source and transfer the heat to the hot body reservoir which acts as a sink and consumes some work.
The entire mechanism of the heat pump is shown in the diagram below.

Refrigerators work on the principle of heat pump, hence when the door is kept open room temperature is high. In order to cool the room it will take heat from the room and some work will be added to it and more heat is released to the room itself. Hence room temperature increases a lot and room becomes too hot.

So, the correct answer is “Option B”.

Note:
Naturally heat transfers from hot body to cold body, but in case of heat pump we are going against nature by transferring the heat from the low temperature body to high temperature body, so we need to do some work on the heat pump to get the required task done.