Correct Answer - Option 3 : Radiation
Explanation:
Heat transfer
The science that deals with the determination of the rate of such energy transfer due to temperature difference are known as heat transfer.
Mode of heat transfer:
Radiation
- Radiation is the energy emitted by matter in the form of electromagnetic waves.
- Unlike conduction and convection, heat transfer in radiation doesn’t require a medium.
- The heat from the sun reaches the earth via a radiation mode of heat transfer.
- The governing equation for radiation is given by:
Q̇ = σAT4
where σ = Stefan-Boltzmann constant = 5.67 × 10-8 W/m2K4
Conduction:
- The mechanism of heat transfer due to temperature difference in a stationary medium is known as conduction.
- In solids, conduction is due to lattice vibration and the free flow of electrons.
- The governing equation for conduction is given by Fourier's law.
\(̇ Q = - \frac{{kAdT}}{{dx}}\)
where k is the thermal conductivity of the material.
Convection:
- It is a mode of heat transfer between a solid surface and an adjacent liquid or gas substance that is in motion.
- It is possible only in a fluid medium where the mass motion of fluid occurs.
- The governing equation for convection is given by Newton’s law of cooling.
Q̇ = hAΔT
where h is the convective heat transfer coefficient.
