Classification of Fixed Resistance:
On the basis of the resistance type or fabrication technique adopted for its manufacture, fixed resistance are classifies as following
1. Carbon Composition Resistors
2. Carbon Film Resistors
3. Metal Film Resistors
4. Wirewound Resistors
In carbon composition resistors the resistance element is a slug of resistive material (carbon in this case) while in film resistors, it is a comparatively thin layer of resistive material painted or deposited on a ceramic or glass-tube. The resistive material is carbon in carbon-film and metal, metal-alloy or metal oxide in case of metal film resistors. In a wirewound resistor, resistive element in length of wire would on an insulating core in one or more than one layers.
Wirewounds resistors are preferred power carbon composition resistors in low resistance, low noise applications.
Significant advantages of carbon composition resistors includes :
1. Very small inherent inductance and capacitance.
2. Do not fail catastrophically.
3. They may withstand higher voltage than film resistors of standard configuration.
Metal film resistors have the reward of both carbon film and precision wirewound resistors without having disadvantages of either.