- No actual movement of molecules takes place.
- Takes place mainly in solid and partially in liquid and gas.(reason > distance between molecules)
- Metals are good conductor of due to presence of free electrons in it.
- Steady state => No heat loss by leakage and rate of flow of heat is same throughout the conductor.
- Non-Steady state = Rate of heat flow varies from point to point. In this case heat loss takes place from body of conductor.
- The rate of fall of temperature with distance in the direction of heat flow is called the temperature gradient.
- Temperature gradient= (Where L is the distance between the point with temperature 1 and 2)
Rate of flow of Heat
- The rate of flow of heat across a cube of side ‘l’ having face of area ‘A’ at different temperature 1 and 2 area depends on
- Area of face of cube
- Temperature difference of opposite faces
- Distances of faces
Where, K is the thermal conductivity of matter of unit whose value depends on nature of conductor
Silver has the highest thermal conductivity.
Where = Rate of flow of heat is called heat current
=Temperature difference is equivalent to potential difference
=R is called the thermal resistance which oppose the flow of heat current
Combination of conductor
Series Combination => = => =
Parallel Combination =>=
Thermal conductivity of a good conductor by searle's method:
Where, K is the thermal conductivity of the rod
Application of Conduction:
- Ice is packed in saw dust(reason: wood and air are bad conductor or heat)
- Woolen clothes are warm because they have fine pores filled with air. (wool and air are bad conductor of heat)
- Eskimos make double walled houses of the blocks of ice. ( air enclosed between the double wall is …..(good/bad) conductor of heat. Ans = bad)