Types Of Resistors

Resistors are electronics component used for resisting the flow of current in a circuit. They also divide the voltage in an electronics circuit.
It is one of the most important passive components of an electronic industry because, without these components, active devices cannot process the electrical signals. Its main purpose is to provide a precise quantity of electrical resistance.

The more the resistance, the more current will be limited and the less current will actually flow. Resistors pay a price for limiting current - they create heat.  In other words, resistors convert electrical energy into heat energy.  

Types of Resistors
1. Fixed resistors
2. Variable resistors

1. Fixed Resistors - 
This are resistor type that have fixed resistance. Although there resistance value can vary with temperature change. There resistance value is determined using there color code or a multimeter.











Resistor are generally used to limit current flow in a circuit.
Consider the following consideration - 

A Light Emitting Diode (LED) that requires 20mA at 3v for operation is to be connected to a 9v power pack. Obviously if we connect the LED directly to the power pack it will burn, to avoid this, a resistor is connected to drop this voltage so that the LED will be able to function properly.

The above table explain how to determine resistor value using its color code.

So, to determine a resistor value with a color code - Orange ,  Red , Black, Gold.














2. Variable Resistor
Variable resistors are resistor that there resistance value can be adjusted by a wiper at its center. It basically consist of 3 parts.
The two resistor pin and a wiper or control knob for varying its resistance.

So, if a variable resistor is rated 10kOhms. 
The resistance value is describe as below. So, as the wiper or control shifts then the resistance begin to change. For instance the picture indicates the wiper to be at the center of the control element (50%) so the resistance between point A and B is 5kOhms each.

Suppose the wiper shifted to a region of 80%/20% percent then resistance value from point A to W will be 8kOhm and from point B to W will be 2kOhm.

3. Thermistor 
Thermistors are semiconductor resistance thermometer used to measure the temperature. These are made of semiconductor compounds such as sulphides,oxides,silicates of Mn,Co,Ni,Fe etc.
A thermistor is a temperature sensing element composed of sintered semiconductor material that exhibits a large change in resistance in proportion to a small change in temperature. 

Thermistors are of two opposite fundamental types:

• With NTC, resistance decreases as temperature rises to protect against inrush over-voltage conditions. Commonly installed in parallel as a current sink.
• With PTC, resistance increases as temperature rises to protect against over-current conditions. Commonly installed in series as a resettable fuse.

Application of Thermistor include but not limited to - Temperature control fan, low temperature thermometer.