A sphere, a cube and a thin circular plate all of same material and same mass initially heated to same high temperature are allowed to cool down under similar conditions. Then the
- plate will cool the fastest and cube the slowest
- sphere will cool the fastest and cube the slowest
- plate will cool the fastest and sphere the slowest
- cube will cool the fastest and plate the slowest
The Correct Option is C
Solution and Explanation
The rate at which an object cools is determined by the surface area and volume.
According to Newton's law of cooling, the rate of heat loss is directly proportional to the surface area and inversely proportional to the volume.
The sphere has the least surface area for a given volume, which makes it lose heat more slowly.
The plate has the greatest surface area relative to its volume, allowing it to cool down the fastest.
The cube has a moderate surface area and will cool at a rate between the sphere and plate.
Thus, the plate will cool the fastest and the sphere the slowest.
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Concepts Used:
Heat Transfer
What is Heat Transfer?
It is defined as the movement of heat across the border of the system due to a difference in temperature between system and its surroundings.
How is Heat Transferred?
Heat can travel from one place to another in several ways. The different modes of heat transfer include:
- Conduction - Heat flows from things with higher temp to objects with lower temp.
- Convection - Movement of liquid molecules from higher temp regions to lower temp regions.
- Radiation - Radiant heat is present in every other way in our daily lives. Thermal radiations are also known to as radiant heat. Thermal radiation is generated by the emission of electromagnetic waves.
