Which option is an example of heat transfer by conduction?
1. Pavement heating up in the sun
2. Person getting warm from an electric blanket
3. Air conditioner cooling the room
4. Air getting warm from a radiator
4. Air getting warm from a radiator
Option 4. Air getting warm from a radiator is an example of heat transfer by conduction.
The correct option that represents an example of heat transfer by conduction is option 4: Air getting warm from a radiator.
To understand why this is the correct answer, let's first discuss what conduction is. Conduction is the transfer of heat through direct contact between particles or objects. In this process, heat energy is transferred from the particles with higher kinetic energy (hotter) to the particles with lower kinetic energy (cooler).
In the given options, option 4 represents conduction because when the air comes into direct contact with a hot radiator, the higher temperature of the radiator causes the particles in the air to gain kinetic energy. This increased kinetic energy leads to an increase in the air temperature, making it warmer.
Let's analyze the other options to understand why they are not examples of heat transfer by conduction:
1. Pavement heating up in the sun: This is an example of heat transfer by radiation. The sun emits electromagnetic waves (radiation), which travel through space and reach the pavement's surface. When these waves are absorbed by the pavement, the energy is converted into heat, causing the pavement to heat up. No direct contact between particles is involved, so it's not conduction.
2. Person getting warm from an electric blanket: This is an example of heat transfer by convection. The electric blanket warms up through electrical resistance, and as the warm air rises from the blanket, it comes into contact with the person's body, transferring heat. This process involves the movement of warm fluids (air in this case) and is hence convection, not conduction.
3. Air conditioner cooling the room: This is an example of heat transfer by convection. The air conditioner cools the room by removing heat from the indoor air and transferring it to the outside. This is done through refrigeration and convection. The cool air produced by the air conditioner circulates in the room, absorbing heat from the surroundings and creating a cooling effect. Again, no direct contact between objects occurs, so it's not conduction.
Therefore, the only option that demonstrates heat transfer by conduction is option 4: Air getting warm from a radiator.