Electric Power - Summary – The Physics Hypertextbook
In physics, power is the rate of doing work or transferring heat, the amount of energy transferred .. These relations are important because they define the maximum performance of a device in terms of velocity ratios determined by its physical. In physics we say that work is done on an object when you transfer energy to that object. Heat Energy -- a form of energy that is transferred by a difference in .. Three variables are of importance in this definition - force, displacement, and. The power transfered by an electric current is the product of its voltage (the " strength" of the Units. The watt is a joule per second (from its definition).
Work, Power, and Energy - Wikiversity
The short way is to combine the formulas, replacing F with mg and using h height in place of d: A mass is moving and can do work when it hits another object. Electrons can flow out of a battery or capacitor and do work on another electrical component such as a light bulb. Although massless, a photon does have energy; in the amount hf where f is the photon's frequency and h is Planck's constant.
This is the energy that warms your face in the morning sun and burns your unguarded nose at the beach.
When some kinds of molecules are combined with others, energy can be released, usually as heat, light, or motion. When coal is burned it releases photon energy stored by plants millions of years before.
When hydrogen combines with oxygen to form water, heat is released as well. A fire is oxygen combining with other substances; this also produces heat. Mixing mentos and coke produces foam whose mechanical properties can be exploited as in a MythBuster's Christmas machine.Relation Between Power and Energy (Physics)
One stick of dynamite produces about a Megajoule. When an atom fissions it releases various particles and a little bit of heat.
This is especially important when you have the current in a much more useful unit like mA. Power is defined in Physics as the ability to do work. In this context this means either to physically move something or generate heat. It is the heat generation properties of power that mainly concerns us here. When current is flowing through something heat is being generated, and this heat has to do somewhere.
It is spread throughout the material and we say it is being dissipated. The up shot is that the material gets hotter, or experiences a temperature rise. The heat causing the rise in temperature flows into the environment and an equilibrium is reached.
The amount of heat that flows depends on the temperature of the environment or ambient temperature and the thermal resistance between the material and the environment. In fact is is very similar to electricity with temperature being equivalent to voltage, current being equivalent to heat and thermal resistance being equivalent to resistance.
Why should I care? You care because you can calculate if something will get too hot and burn out in advance of it happening.
If one end of you thermal resistance is anchored at the ambient temperature the other end gets hotter, the temperature it get to is dependent on the power dissipated and the thermal resistance. You can reduce the latter by applying a heat sink but no amount of heat sink is going to affect the former. In fact manufacturers of devices often use the concept of an infinite heat sink in getting their headline figures.
That means a heat sink so big that the case temperature and the ambient temperature are the same thing. As a rule of thumb: