Basics of Resistors

The Resistor is an electrical component which is used to control the amount of current.

The electrical resistor is the most commonly used component which is used in all consumer electronics. Depending on their applications there are various types of electrical resistors which are available in different sizes.

In this section you'll learn:

  • How a resistor works
  • Symbol of resistor
  • Color-coded resistors
  • Color coding charts
  • Other types of resistors



How it works?

A resistor offers the electrical resistance against current flow. The more the resistance, the lower is the flow of current. This feature allows us to use any value of resistance for controlling the current.

Let's consider a circuit with 10 V source where we want a current of 1 A to flow through the loop. In this case, we can use Ohm's law to find our desired resistor for 1 A current. R = V/I = 10 V/ 1A = 10 ohms.
The figure below further illustrates how we can achieve the desired current by changing the amount of resistance.

Symbol of Resistor

Two models are used for representing the resistors:

Color Coded Resistors

Color-coded resistors are most common types of resistors. These are two terminal components. Their value is indicated by using the colored bands on their bodies. A resistor contains four, five or six bands on the body.

Practically they are used in dc power supplies, mobile phone chargers, lower and medium edge consumer electronics.

The exact values can be found from the color charts.

4 Band Color Coding Chart

5 Band Resistor Color Coding chart


Other types of Resistors

Potentiometer

Potentiometers are the variable resistor whose value of resistance can be varied. A potentiometer is a three-legged device which is used in volume control of receivers and in control of fan speed. The left side of the figure below displays the conventional potentiometers. The other one on the right side displays trimpot which is competitively an advanced model of potentiometers. You can learn more about potentiometers here: Basics of potentiometers

potentiometer


Thermistor

The thermistor is a two-terminal temperature dependent resistor whose amount of resistance changes with the change of temperature.

Thermistors are classified into two main classes the NTC and PTC.

NTC is negative temperature coefficient thermistor whose resistance decreases when the temperature increases.

PTC is the positive temperature coefficient device whose resistance increases when the temperature decreases.

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