Write two difference between conduction and convection
Answers
RADIATION
Meaning Conduction is a process in which transfer of heat takes place between objects by direct contact. Convection refers to the form of heat transfer in which energy transition occurs within the fluid. Radition alludes to the mechanism in which heat is transmitted without any physical contact between objects.
Represent How heat travels between objects in direct contact. How heat passes through fluids. How heat flows through empty spaces.
Cause Due to temperature difference. Due to density difference. Occurs from all objects, at temperature greater than 0 K.
Occurence Occurs in solids, through molecular collisions. Occurs in fluids, by actual flow of matter. Occurs at a distance and does not heats the intervening substance.
Transfer of heat Uses heated solid substance. Uses intermediate substance. Uses electromagnetic waves.
Speed Slow Slow Fast
Law of reflection and refraction Does not follow Does not follow
CONDUCTION
Conduction is a process of heat transfer which occur in solid, liquid and gases. In conduction energy is trasfer when molecule of higher energy collide with the molecule of lower energy. In solid, molecules vibrate at there lattice position and transfer their energy from higher tempreature molecule to lower energy molecule. In solid( metals) 70% of conduction occur through transfer of electrons and 30% occur through molecular vibration. In metals heat transfer decreases with increase in tempreature as electron transfer is obstructed by the vibration of molecules while in non metals heat transfer increases as molecular vibration increases. In gases and liquid heat transfer also increases with increase in tempreature.
Heat transfer through solid in a particular direction is directly propotinal to the tempreature gradient in that direction ( Fourier law of conduction )
CONVECTION
It is a process of heat transfer in which the molecule of higher energy move towards the region of lower energy. It occur in liquid and gases, but not in solid. This molecule can transfer naturally or forcefully. In natural convection molecule at higher tempreature region become lighter than molecule at lower tempreature and thus due to bouyancy effect molecule of higher tempreature move upward and molecule of lower tempreature move downward. while in force convection molecules are moved forcefully and thus this will increase the heat transfer.Heat transfer depend on surface area, tempreature diffrence and condition of medium in which convection is going to occur.