Question

There are two solar energy collectors made up of thin aluminium sheets. They are flat and uncoated. Collector ‘A’ is rectangular measuring 20 cm long and 15 cm wide while collector ‘B’ is circular having 20 cm diameter. If they are kept under mid-day sun for a long time then,
A. Both the collectors A and B will show nearly the same temperature
B. Collector A will show a higher temperature than B.
C. Collector B will show a higher temperature than A.
D. There will be no rise in the temperature of the two collectors, as they are uncoated.

Answer 1

Hint: Aluminum is a good conductor of heat and electricity. The temperature is a physical quantity that depends on the type of material and does not depend on the area of exposure. Using these properties we will answer the question.

Complete answer:
From the given information, we have the data as follows.
There are two solar energy collectors made up of thin aluminium sheets. They are flat and uncoated. Collector ‘A’ is rectangular measuring 20 cm long and 15 cm wide while collector ‘B’ is circular having 20 cm diameter.
The properties of aluminium: It is a very good conductor of heat and electricity. It is a silvery-white metal with a bluish tinge and it exhibits bright lustre on a freshly broken surface. It is a non-magnetic substance. It is highly resistant to corrosion. The metal is highly ductile and reflective, impermeable and odourless.
The temperature is a physical quantity that depends on the type of material and does not depend on the area of exposure. The temperature measures the physical property of ‘how cold’ or ‘how hot’ the material is.
Both the collectors are made up of aluminium. As the collector is made up of aluminium and aluminium is a good conductor of heat and electricity, thus, both the collectors will absorb heat.
So, both collectors A and B will show nearly the same temperature.
\[\therefore \] There will rise in the temperature of the two collectors, that too of equal amount.

Thus, option (A) is correct.

Note:
As the temperature of a body depends on the type of material and not on the area of exposure, thus, if the 2 objects are made up of the same material, then, there will be an equal amount of rising in temperature.