# Newton’s Law of Cooling & Fourier’s Law of Heat Conduction- Heat Transfer

### Newton’s Law of Cooling :

The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. the statement is called Newton’s law of cooling.

### Fourier’s Law of Heat Conduction :

It is an important law in heat conduction, which is represented by the equation,….

Q ∝ A x dT / dx ⇒ Q = k A x dT / dx

where ,           Q= Amount of heat flow through the body in a unit time,

A= Surface area of heat flow, taken at the right angle to the direction of the  flow,

dT= Temperature difference on the two faces of the body,

dx= Thickness of the body through which the heat flow, taken along the direction of heat flow, and

k= Constant of proportionality known as the thermal conductivity of the body.

From above, we see that amount of heat flow through a body by conduction is,…..

1.  Directly proportional to the surface area of the body,
2.  Directly proportional to the temperature difference on the two faces of the body,
3.  Inversely proportional to the thickness of the body, and
4.  Dependent upon the material of the body.