What is a Carbon Resistor?
Carbon Resistor Definition: Carbon is a non-metallic and ideal material for making a resistor. Resistors made of carbon or graphite are called carbon resistors.
A carbon resistor is a passive electronic device used to produce a fixed resistance opposition on a circuit, the carbon resistor is made with carbon granules.
Making of carbon resistor is using carbon powder granules, the carbon is less expensive and also carbon-based resistors ensure 90-95% accuracy on-resistance values.
Different types of materials such as nichrome, brass, platinum, and many metal alloys also produce high resistance, but most of these material based resistors produce very low resistance values compared to carbon resistor and also resistivity of material purely based on length and width of the material, so making a resistor using this material will be extremely difficult than a carbon-based resistor.
The resistivity of graphites is only 2.7 ohm-centimeters (0.0039 ohms-cm). The graphitic nature of the carbon makes the material very lightweight and flexible.
Carbon resistances are commonly used in audio and video circuits, where high resistance is needed to minimize noise.
Carbon has low cost and ease of use, carbon has become a popular material used at making resistor
It has a number of properties that make it ideal for the design of electrical devices. The primary advantage of carbon is its high resistivity.
Resistance is the amount of current that flows through the material per unit of time. This property can be used in many different ways to make electrical components.
Parts of a Carbon Resistor
- Ceramic core
- Carbon film
- Nickel Cap
- Copper lead
- Protective epoxy layer
Carbon Resistor Symbol
The carbon resistor is a fixed resistor type is the symbol is a normally fixed resistor
types of a carbon resistor
- Carbon composition resistors
- Carbon film resistor
Carbon composition resistors
Resistors made by compressing carbon powder while using a suitable resin binder are called composition resistors. They are of the following two types:
- Pallet or Slug Type. For making this type of resistor, carbon black or graphite powder is molded into small cylindrical pieces while using a suitable resin binder. During molding, two leads of tinned copper wire are also joined, one on each side. A protective coating is made of over-molded pieces. After heat treatment, the resistor becomes ready for use.
- Filament Type Carbon Composition Resistor. For making this type of resistor, carbon powder is deposited over a porcelain or glass tube with the help of a resin binder. Tinned copper leads are joined on both ends, one on each side. Finally, the resistor is covered with a phenolic (weatherproof) layer.
Carbon composition resistors are made in the range of 2 ohms to 10 mega ohms with 1/8, 1/4, 1/2, 1, and 2 watts power ratings.
Carbon film resistor.
These types of resistors are made by depositing hydrocarbon vapours on a ceramic capillary pipe at 900- 1100°C temperature. Resistors of small values are made by depositing metallic oxide (of palladium, nickel, chromium metals) on a ceramic capillary pipe. Resistors of the first type are also known as pyrolytic resistors and of the second type as metal oxide film resistors. Tinned copper or silver wires are used as leads for these resistors.
These types of resistors are made in the range of 1 ohm to 20 mega ohms with 1/2 watts power rating.
advantage of Carbon Resistors
- Their size may be quite small up to 6 mm x 1 mm
- their mass may be quite small up to 1 gram
- the high-value resistor can be made easily
- they are most suitable for high-frequency circuits
- their temperature coefficient lies within 0.02 to 0.1
disadvantage Carbon of Resistors
- temperature and humidity affect their values
- their current charring capacity is limited since their wattage is limited up to 2 watt
- their stability and reliability are poor
- it is difficult to make a carbon resistor of a value below 2 ohms