Heat conduction and convection

We all cook food at our home

In cooking, we heat food items. It destroys microorganisms, making it safe to consume

When food becomes hot, its molecules absorb energy and begin vibrating rapidly

As they collide, heat energy is produced and transferred, which warms up food

This happens due to physical phenomenon called heat transfer

So let’s see more about heat transfer

Heat transfer

Heat transfer is exchange of thermal energy between two objects

There are three different modes of heat transfer which are used while cooking

In cooking, burners on stoves conduct heat to the bottom of pan, from there the pan conducts heat

The pan conducts heat by using the mode of heat transfer called conduction

Conduction

Conduction is the process of heat being transferred between objects through direct contact

During conduction the matter itself does not flow, rather heat is transferred by vibrations of atoms

It does not involve motion of matter, it is transfer of energy between objects in contact

The equation governing the rate of heat transfer through conduction is as above

In equation 'k' is the thermal conductivity

The direct contact between the cooking surface and stove allows food to be cooked

Now let’s see the mode of heat transfer in which we observe movement of matter

Convection

The molecules close to heat source become warm, they rise and are replaced by cooler ones

This creates a circulating current that evenly distributes heat throughout

This mode of heat transfer is called convection and is usually used by fluids

Convection currents are set up in fluid because hotter part of the fluid is not as dense as cooler part

There is upward buoyant force on the hotter fluid, making it rise while the cooler fluid sinks

There is one more mode of heat transfer which is used in cooking called radiation

Radiation is the process where heat and light waves strike and penetrate hence cooks the food

Revision

Heat transfer is an exchange of thermal energy between two objects

Conduction is the process of heat being transferred between objects through direct contact

Convection currents are set up because hotter part of fluid is not as dense as cooler part

Radiation is the process where heat and light waves strike and penetrate over the body

The End