Transfer of Heat- Three Ways of Heat Transfer

Transfer of Heat

 Key Concepts

1. Transfer of heat
2. The direction of heat flow
3. Conduction
4. Convection
5. Radiation

Explanation

Heat transfer: 

Heat transfer is a process where the heat energy is transferred from one body to the other regardless of the contact the body is in or not. Hence heat transfer has three different ways. 

The direction of Heat transfer: 

Heat always transfers from the hot body to the cold body. 

Points to be remembered: 

1. The direction of heat transfer is always from the hot body to the cold body. 

2. The heat transfer will continue until the bodies attain a thermal equilibrium. 

3. Thermal equilibrium is achieved when bodies under heat transfer are at the same temperature. 

Heat can be transferred in three ways 

1. Conduction 

2. Convection 

3. Radiation 

Conduction 

Let us consider a pan on the stove and turn on the heat. 

What do you observe? 

When the pan is on the stove, and the stove is heated up. After some time, you can see that the pan is getting heated up and the material inside the pan is also getting heated up and it is observed that the pan is not getting burnt up. 

Hence conduction is the transfer of heat from the hot body to the cold body when the bodies are in contact with each other. 

Points to remember: 

1. Conduction is the process of heat transfer without burning the material  

2. Bodies in conduction should be in contact 

3. Heat in conduction requires a medium to transfer like solids 

4. The flow of heat/direction of heat is always from a hot body to a cold body 

Examples: 

1. Iron box 

2. Pan on a stove 

3. Kettle ETC 

Convection: 

Consider an AC in the room. If the AC is switched on, the room will be getting more relaxed, and the temperature inside the room drops because the particles of low heat are traveling in the environment (air). 

Convection is the process of heat transfer in liquids and gases, where the direct physical contact is not necessary for heat flow. 

Points to remember: 

1. Convection is the process of heat transfer where direct contact is not necessary. 

2. Convection occurs mainly in fluids (liquids and gases). 

3. Heat transfer requires a medium to transfer like liquids and gases. 

4. The flow of heat is always from the hot body to the cold body. 

Examples: 

1. AC or heater in the room 

2. Steam bath 

Radiation: 

We all know that the sun is the natural source of heat and light. The source of heat energy is transferred in the form of radiation. 

Hence radiation of heat transfer doesn’t need a medium to propagate like solids, liquids and gases. 

Important points to remember: 

1. Radiation is the process of heat transfer 

2. Radiation doesn’t require a medium to propagate 

3. The flow of heat is always from the hot body to the cold body 

Examples: 

1. Sun 

2. Black body 

Summary

Heat transfer:

Heat transfer is a process where the heat energy is transferred from one body to the other regardless of the contact the body is in or not. Hence, the heat transfer has three different ways.

Conduction is the transfer of heat from the hot body to the cold body when the bodies are in contact with each other.

Points to remember.

1. Conduction is the process of heat transfer without burning the material
2. Bodies in conduction should be in contact.
3. Heat in conduction requires a medium to transfer like solids
4. The flow of heat/direction of heat is always from a hot body to a cold body.

Convection is the process of heat transfer in liquids and gases, where direct physical contact is not necessary for heat flow.

Points to remember.

1. Convection is the process of heat transfer where the direct contact is not necessary
2. Convection occurs mainly in fluids (liquids and gases)
3. Heat transfer requires a medium to transfer like liquids and gases
4. The flow of heat is always from a hot body to a cold body
   

Radiation of heat transfer doesn’t need a medium to propagate like solids, liquids and gases.
Important points to remember:

1. Radiation is the process of heat transfer
2. Radiation doesn’t require a medium to propagate
3. The flow of heat is always from a hot body to a cold body