Hi Guys, here in this article you will get details about an important electronic component “Resistor”. Resistor is an important and basic element of every electronic circuit. Without a resistor you can’t imagine Ohm`s Law.
What is a Resistor?
Resistor is an electronic component. In electronic circuit its resistance is used to limit current or for better understanding it limits flow of electron. It is a passive element means it consume power. Resistor is used in every electronic and integrated circuit. Mostly resistors are used to set up different voltages level in circuit and to limit current.
Resistance of a resistor is measured in Ohms. Symbol of Resistor is Ohm Ω (Greek letter Omega). The definition of 1Ω Omega is the resistance between two point where voltage in 1 Volt DC and current is also 1 Ampere.
In a circuit resistance is denoted by “R”. Symbol of resistor is a zig-zag line as shown in figure. This zig-zag pattern is American Pattern. It also can be shown in a two terminal box in circuit diagram or schematic. This box pattern is international pattern.
How Many types of Resistors are available in Market?
In market a variety of resistor is available. We can distinguish these resistors on the basis of its termination and Mounting. In market Resistor may be a static resistor, a pack of resistors, or a special variable resistor.
Resistor types (On the basis of its termination & mounting style)
On the basis of mounting style Resistors are available in two types through hole and surface mount.
Through hole type Resistor
It is also called ceramic resistor. As shown in figure it has a cylindrical body with two terminals. Its cylindrical body is printed with colour band which is used to identify resistor value. It can be easily used with Bread-Board or can be soldered in a printed circuit board. Thickness of cylindrical body depends on the Resistor power rating. Normally a 1/2W Resistor thickness is around 9-10 mm and a 1/4W Resistor thickness 6-7 mm.
Surface-mount type Resistor
These Resistors are usually in a shape of small rectangles. Its terminals are also very small. These resistors can’t be used in a bread board or in a PCB manually. It required a specific machine to mount on PCB. Usually you can find in on Computer Mother board. Its value is printed on resistor body and can be see with a magnifying glass.
Other Resistors (Special Purpose)
Through-hole and surface-mount resistor are general resistors and can be used in variety of application. But in market special purpose Resistor is also available. These are called Potentiometer and resistance array etc.
Potentio-meter is a variable resistor. We can change its resistance value manually. It can be adjust within a specific range. It also called Rheostat.
This resistor is a special purpose resistor. It comes with 5-6 terminals. Generally it is used to set up different voltage level in a Circuit.
Construction of a Resistor
Construction material of a resistor is generally Carbon & Metal Oxide and for termination Aluminum Metal. As shown in figure a thin film of resistive material is wrapped in helical format over a ceramic cylinder.
In Surface-mount resistors a resistive material strip is sandwiched between ceramic case. And its terminal is connected with conductive material. SMD resistors are available in thick or thin-film variety. Thick-film is usually cheaper but less precise than thin film technology.
Handling Resistor Heat in Circuit
As you know that Resistor is a passive device and it consume power. This power convert in to Heat and it may cause burn in your circuit. So the question is how to avoid this heat? And its answer is you can’t avoid heat but you can avoid burn or fire in you resistor. To understand it first understands Power Rating of a Resistor.
Each and every resistor has a specific power rating. It is its maximum power capacity. In order to keep the resistor from heating up too much, it’s important to make sure the power across a resistor is lower than its Power Rating. The power rating of a resistor is measured in watts, and it’s usually somewhere between ⅛W (0.125W) and 1W.
Resistors with power ratings of more than 1W are usually referred to as power resistors, and are used specifically for their power dissipating abilities. That`s why we are using a small cooler fan in computer motherboard.