Let be an additional periodic force apart from the restoring force and the damping force,
then Amplitude in forced oscillation given by
Where is called a natural angular frequency.
and is the angular frequency of the driving force.
It is called the "zeroth" law because it came to light after the first and second laws of thermodynamics had already been established and named, but was considered more fundamental and thus was given a lower number , i.e zero.
The ratio of two extensive properties of the same object or system is an intensive property. For example, the ratio of an object's mass and volume is called density, And density is an intensive property. But both object's mass and volume are extensive properties.
Electricity is a general word used to explain phenomena caused due to charge under rest or motion. In electrostatic we study about charge under rest and in current electricity we study about the flow of electric charge through a region.
Wien's displacement law is useful for determining the temperatures of hot radiant objects such as stars, and it is also useful for a determination of the temperature of any radiant object whose temperature is far above that of its surroundings.
According to Kirchhoff's law, the ratio of emissive power to absorptive power is the same for all surfaces at the same temperature and is equal to the emissive power of a perfectly black body at that temperature.
And as for perfectly black body A = 1