Question

1)conduition of heat 2) convection of heat​

Answer 1

Answer:

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Explanation:

answer no.1 Whenever there is a temperature difference, there is a transfer of heat energy occuring between two material bodies.

Conditions for the transfer of heat energy to occur:

Condition 1:

Material bodies in contact with a difference in their temperatures.

Heat energy is always transferred from a higher temperature region to a lower temperature region.

Mechanism of conduction in a gas :

In a higher temperature region, the molecules of a particular gas have higher velocities, move in a continuous random motion, colliding with each other and exchanging a great amount of energy and momentum.

Therefore if a molecule moves from a higher temperature region to a lower temperature region, kinetic energy is transferred to the lower temperature region and this energy transfer takes place until the system attains an equilibrium temperature.

Condition 2:

Material bodies may not be in contact with each other.

Mechanism of convection between a hot metal plate and air/fan :

Hot metal plate kept under a fan cools faster when compared to the hot metal plate in still air.

Here, Heat is convected.

The temperature gradient is dependent upon the rate at which the fluid carries the heat away.

Heat transferred from the hot metal plate to the fluid at the wall of the plate is obviously a conduction process, but overall the entire transfer of heat is a convective process.

Convection heat transfer depends upon the viscosity of the fluid and also the thermal properties such as conductivity, specific heat, density etc

Condition 3:

Heat transfer also occurs in a region where perfect vacuum exists.

Mechanism of radiation:

Electromagnetic radiation which occurs due to temperature difference is called thermal radiation.

ans 2.

Convection is the transfer of heat due to the bulk movement of molecules within fluids (gases and liquids), including molten rock (rheid). Convection includes sub-mechanisms of advection (directional bulk-flow transfer of heat), and diffusion (non-directional transfer of energy or mass particles along a concentration gradient).