Question

the three mechanisms of heat transfer (conduction, convection, radiation). How could it be improved? HINT: In your own words, define conduction, convection, and radiation.

Answer 1

First, let us define the three modes of heat transfer: Conduction, Convection and Radiation:

Conduction: This mode of heat transfer occurs when solid materials/objects are the medium of heat exchange. For example:

> directly touching a hot vessel in the kitchen

> during ironing of clothes

Convection: This mode of heat transfer occurs when fluids (liquids or gases) are the medium of heat exchange. For example:

> mixing of cold milk in a cup of hot tea

> a heat blower warming an entire room

Radiation: This mode of heat transfer occurs when no medium is present for the heat exchange, and the heat travels via electromagnetic waves. For example:

> feeling the warmth of direct sunlight in your car even with closed windows

Performance of a calorimeter is dependent on how well it contains the heat within itself, i.e. minimize the heat loss to its surroundings. So its design is such that all the three modes of heat transfer can be avoided or minimized.

Heat loss from conduction can be minimized by reducing its contact with the surroundings, eg. instead of placing it on a surface, suspend it via leather straps from top.

Heat loss from convection (to the surrounding air) can be minimized by insulating the walls with materials like polystyrene, or cotton wool. Also by keeping the top of the calorimeter covered with a lid.

Heat loss from radiation can be minimized by using a highly polished calorimeter, i.e. keeping the surface as even as possible, and further by gold plating.