Resistor

Resistors are the basic components of electronics to limit the current flowing in the circuit. Resistor is resistive and is generally made of carbon. From Ohm's law: resistance is inversely proportional to the amount of current flowing through it. Unit resistance of a resistor is called Ohm or represented by the symbol Ω (Omega). Various kinds of resistors made of different materials with properties different. Other specifications that need to be considered in choosing a design resitor is great power. Because resistors working with electrified, there will be a power dissipation of heat for W = I ² R watts. The greater the physical size of the resistor indicates the greater ability of the resistor power dissipation. Generally in the market available sizes 1 / 8, 1 / 4, 1, 2, 5, 10 and 20 watts. Resistor which has a power dissipation of 5, 10 and 20 watts generally cubic-shaped elongated white square, but there is also a cylindrical. But usually for large resistor resistance value printed directly in body, for example, 100Ω 5W.
Resistor based on the Types of Materials and Construction
Based on the type of materials used to make resistors are divided into wire resistors, resistors charcoal and metal oxide resistors. While charcoal resistors and metal oxide resistors based on the known structure composition resistors and resistor films. However, in the resistor market is divided into fixed resistor (fixed resistor) and a variable resistor.
Use for low power are the main types of fixed resistors are resistors printed carbon mixture. The relative size of all fixed resistors and no permanent change to the power rating (the number of watts), the addition of measures to increase the power rating in order to maintain the current and power loss lesapan more big.Resistor variables, has a terminal that can be changed in value and is often called a potentiometer or rheostat.kinds fixed resistor types:
-Metal Film Resistor
-Metal Oxide Resistor
-Carbon Film Resistor
-Ceramic Encased Wirewounde.
-Economy Wirewound
Zero-Ohm Jumper Wire
S I P-Resistor Network
Various kinds of variable resistors:
-Potentiometer:

1.Linier
2.Logaritmis
* Trimer-Potentiometer
* Thermister:
1.NTC (Negative Temperature Coefisient)
2.PTC (Positive Temperature Coefisient)
* DR
* VDR
Resistor Characteristics
Resistor characteristics are influenced by the materials used, if the temperature rises the resistance down. The resistance of a resistor with a different composition of the measured values differ from nominal resistance. If the difference in value to less than 10% of both the circuits that require high precision. Variable resistor changes its resistance in accordance with the change of settings, for example by mechanical control, regulation by light, temperature regulation, or other settings. If the value changes, the resistance of the potentiometer is proportional to the position of the sliding contact of this kind is called a potentiometer linear potentiometer. But if the change in resistance value is not comparable to the position of sliding contact is called potensio logarithmically.
In theory a resistor has a resistance of pure declared but in practice a resistor has the additional properties of inductive and capacitive properties. Basically low value resistors tend to have an inductive nature and high value resistor resistor capacitive.Temperature have additional properties have a significant impact on an obstacle. In conducting a number of free electrons is very large, and any heat energy is applied to it will have little impact on the total number of free carriers. In fact the heat energy will only increase the intensity of the random movement of particles within the material making it difficult for the general flow of electrons in any one direction is determined. The result is good for the conductor, increasing the temperature increase in the price will produce prisoners. As a result, conductor has a temperature coefficient positive.flow → heat HR = I ² Rt [joule] Q = mc (Ta-T) Q = 0:24 I ² R t [calories].