Thermodynamics

Thermodynamics States About Energy Conversion Thermodynamics is the branch of science that embodies the principles of energy transformation in macroscopic systems. The general restrictions which experience has shown to apply to all such transformations are known as the laws of thermodynamics. These laws are primitive; they cannot be derived from anything more basic. The first law of thermodynamics states that energy is conserved; that, although it can be altered in form and transferred from one place to another, the total quantity remains constant. Thus, the first law of thermodynamics depends on the concept of energy; but, conversely, energy is an essential thermodynamic function because it allows the first law to be formulated. This coupling is characteristic of the primitive concepts of thermodynamics. The words system and surroundings are similarly coupled. A system is taken to be any object, any quantity of matter, any region, and so on, selected for study and set apart (men

Magnet and Magnetism

A magnet is a body composed of ferromagnetic or ferrimagnetic material. If suspended in a magnetic field, a magnet will align itself along the field like a magnetic compass in the Earth's field. A magnet has two poles. called north and south, with the property that unlike poles attract and like poles repel one another. The principal physical characteristic of a magnet is that a high concentration of lines of magnetic force pass through its body, doe to the alignment of its constituent atomic magnetic dipoles. This leads to a relatively strong field in the external space, or gap, between poles. The physical properties of a magnet can be explained in terms of the fundamental principles of magnetism.


A permanent magnet is prepared by initially being a removed or turned off, the magnet retains its magnetization for a long time. Permanent magnets are made from alloys and compounds of ferromagnetic metals, mainly iron, nickel and cobalt. Alnico, Alcomax, and Triconal are commonly used as permanent magnet materials. Extremely strong magnets are now being made from compounds of ferromagnetic metals with rare-earth metals.


An electromagnet must be excited continuously by an external magnetic field in order to maintain its magnetism. If the external field is turned off, the magnetism collapse almost completely. Since the 1960s much higher magnetic fields than are obtainable with ordinary electromagnets have been possible through the development of superconducting solenoids, which do not require iron cores.