Introduction to Resistors

  • resistor is a two-terminal device that is used to resist the flow of current. It is one of the most commonly used components in electrical circuits.
  • Resistance of any resister is described in ohms. Ohm is denoted by the Greek letter omega. Each resister has a different value of resistance which tells us how strongly it resists the flow of current. More the value of resistance more is the capability of resisting the current.
  • Resistance will be considered as one ohm if the potential difference between the two ends of the conductor is 1 V and a current flowing through it is 1 Ampere.
  • Resistance can be derived from Ohm’s law which indicates voltage is directly proportional to the current flowing through the conductor.

V= I * R

  • Each resistor comes with two wires, also called as leads. Between these two leads there lies a ceramic part which actually resists the flow of current.
  • Resistor consists of three colored strips that indicate the value of resistance.
  • Some resistors come with four colored strips. In such case, fourth strip indicates the value of tolerance. Tolerance is the value of the deviation of resistance from its given value on the resistor. Gold color of forth strip indicates tolerance is 5% and silver color indicates tolerance is 10%. Where there is no forth strip, tolerance is considered as 20%. Suppose, if resistance has 50-ohm resistance with no forth strip. Then tolerance of such resistor can be 50 ±20%.
  • Resistors also indicate temperature coefficient. Temperature coefficient is known as a resistance due to the change in temperature. There are two types of temperature coefficients. Positive temperature coefficient and negative temperature coefficient. If resistance increases with the increase in temperature then it is called positive temperature coefficient and if resistance decreases with the decrease in temperature then it is called negative temperature coefficient.

How to Calculate Resistance of any Resistor

There are two different ways to calculate the resistance:

Reading the Color Bands
  • First method to calculate the resistance is by reading the color bands of the resistor.
  • Each strip of color on the resistor represents a specific digit.
  • Different colors corresponding to their digit values are given below.
  • In the above figure, the first strip is brown and corresponding digit to brown is 1.
  • The second strip is black, and the corresponding digit to black is 0.
  • The third strip is orange and the corresponding digit to orange is three which actually shows the number of zeros.
  • Forth strip is made of gold which indicates tolerance is ±5%.
  • So overall resistance of this resistor is 10,000±5 % ohm.
Using a Multimeter
  • Second method to measure the resistance is by using the multimeter as an ohmmeter. Mainly multimeter performs three functions. It is used to measure current voltage and resistance.
  • Put the black probe on the COM port of multimeter. And put the red probe into the VΩmA.
  • You can measure the resistance of any resistor by holding the resistor with the two separate probes of the multimeter. Before calculating the resistance, you need to set the dial to ohm which is denoted on the multimeter by the symbol Ω.
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