|
Energy
Everyone knows that energy is neither created nor destroyed. It changes from one form to another form. No wonder, nobody knows how this energy existed in first place. Based on available evidence, we shall see this later, Big Bang theory rules over Steady State theory at present.
There are various types of energy exist in the form of potential energy and kinetic energy. The stored energy is known as potential energy where as kinetic energy is present in any moving objects or living things.
Types of energy are as follows:
Kinetic energy
Electrical energy
Thermal or heat energy
Nuclear energy
Light energy
Sound energy
Potential energies are as follows
Gravitational potential energy
Chemical potential energy
Elastic potential energy.
Heat or Thermal energy:
Heat is a lost energy in most places but it is very useful energy too. Heat is generated and transferred from one place to another. This heat is transferred in three ways:
Conduction
Convection
Radiation
Conduction
Conduction occurs in solids where free movement of electrons are present. When a metal is heated, the electrons vibrate more rapidly and gain more kinetic energy. As these electrons move around and collide with other free electrons and gain further more energy. Thus kinetic energy is therefore transferred between the electrons thereby heat is transferring from one point to another very quickly.
Conduction does not occur in non-metals as there are no free electrons are present whereas as atoms vibrate in metals and in insulators heat is conducted. Atoms absorb thermal energy and vibrate more rapidly and make other atoms vibrate more.
Convection
It happens in liquids and gases. When heated the cool particles gain kinetic energy. It expands and become more dense therefore they fall and move towards the heat source to take the place of the warm particles. The cycle continues so cool particles heated up.
Radiation
Energy from the Sun to Earth occurs in the form of radiation as electromagnetic waves. As there is no solid medium and liquid or air medium, conduction and convection were not possible. Thus radiation occurs even through vacuum.
Electromagnetic waves are absorbed, reflected and transmitted when it falls on an object. All objects emit and absorb thermal radiation. As the object gains more heat energy it radiates more energy therefore dark, matt surfaces are good absorbers and good emitters of radiation whereas light, shiny surfaces are poor absorbers and poor emitters of radiation.
The transfer of heat in the object depends on the shape and dimensions of that object. This also depends on temperature difference between an object and its surroundings.
2 |
