The first time when a person learns about electricity, you will learn that materials fall under two basic categories; which are:
• Conductors: These are materials that allow electricity to pass through easily. They include materials such as metal, copper, and others.
• Insulators: These are materials that do not allow electricity to pass through. they include materials such as wood, plastic, air and others.
However, nothing is so simple, is it? Do you know that any substance will conduct electricity if you apply a big enough voltage across it? Lightening occurs even if air is an insulator. Powerful voltage builds up in the clouds, which eventually travels through the air.
In order for a material to allow electricity to pass through, its resistance capabilities must be exceeded. In other words, resistance is the ease of which a material will let electricity flow through it. With this information, it is straight forward that all conductors have low electric resistance, whereas all insulators have high resistance.
Devices known as resistors lets us introduce precise and controlled amount of resistance to an electric circuit.
What Is A Resistor?
A resistor is a passive electrical component that is used to create resistance in electric current flow. These devices can be found in almost all electronic and electrical circuits. Resistance is measured in Ohms. Device resistance is derived from the number of voltage divided by current. Resistors are used for many purposes. Few examples include: voltage division, electric current, heat generation, control gain, loading circuits, fixing time constants and much more.
Resistor Groups and Types
A resistor can only be categorized into two groups, which are: Variable and Fixed vale resistor
1. Fixed Value Resistor Types
Fixed value resistors can be classified into the following groups
• Carbon Composition Resistor : These kind of resistors are derived from graphite paste or carbon dust (best for low wattage value circuits)
• Cermet or Film Resistor : These resistors are derived from metal oxide paste (best for very low wattage values)
• Wire-Wound Resistor : These kind of resistors are made from metallic bodies. They mainly go together with heatsinks. (best for very high wattage ratings)
• Semiconductor Resistor : These kind of resistors are made from high frequency and precision surface mounts thin film technology
It is important to note that there are many fixed resistor types. Moreover, each group resistors are constructed differently, with each resistor acquiring its own characteristic, merits and limitations.
2. Variable Resistors
A variable resistor has both a fixed resistor and a slider that is connected to the main resistor’s element. This means that they come with three connections of electrical components. Two connections are connected to the fixed element. This means that they have a fixed resistance value. The third connection will act as potential variable divider, only if all the connections are used. At the same time, a person may prefer to use only two connections: i.e. one of the ends of the resistor and the third connection slider.
There is plenty more to learn about resistors such as how size affect resistance, how to read resistance using color codes, and much more.