Resistor Tutorial Summary

We can summarize this resistor tutorial section and what we have learnt as follows:

resistor tutorial
  • The job of a Resistor is to limit the current flowing through an electrical circuit.
  • Resistance is measured in Ohm’s and is given the symbol Ω
  • Carbon, Film and Wirewound are all types of resistors.
  • Resistor colour codes are used to identify the resistance and tolerance rating of small resistors.
  • The BS1852 Standard uses letters and is used to identify large size resistors.
  • Tolerance is the percentage measure of the accuracy of a resistor from its preferred value with the E6 (20%), E12 (10%), E24 (5%) and E96 (1%) series of tolerance values available.

Series Resistor Tutorial

  • Resistors that are daisy chained together in a single line are said to be connected in SERIES.
  • Series connected resistors have a common Current flowing through them.
  • Itotal = I1 = I2 = I3 …. etc

  • The total circuit resistance of series resistors is equal to:
  • Rtotal = R1 + R2 + R3 + ….. Rn etc.
  • Total circuit voltage is equal to the sum of all the individual voltage drops.
  • Vtotal = V1 + V2 + V3 …. etc

  • The total resistance of a series connected circuit will always be greater than the highest value resistor.

Parallel Resistor Tutorial

  • Resistors that have both of their respective terminals connected to each terminal of another resistor or resistors are said to be connected in PARALLEL.
  • Parallel resistors have a common Voltage across them.
  • VS = V1 = V2 = V3 …. etc

  • Total resistance of a parallel circuit is equal to:
  • parallel resistance equation
  • Total circuit current flow is equal to the sum of all the individual branch currents added together.
  • Itotal = I1 + I2 + I3 …. etc

  • The total resistance of a parallel circuit will always be less than the value of the smallest resistor.

Resistor Power Rating

  • The larger the power rating, the greater the physical size of the resistor to dissipate the heat.
  • All resistors have a maximum power rating and if exceeded will result in the resistor overheating and becoming damaged.
  • Standard resistor power rating sizes are 1/8 W, 1/4 W, 1/2 W, 1 W, and 2 W.
  • Low ohmic value power resistors are generally used for current sensing or power supply applications.
  • The power rating of resistors can be calculated using the formula:
  • resistor power equation
  • In AC Circuits the voltage and current flowing in a pure resistor are always “in-phase” producing 0o phase shift..
  • When used in AC Circuits the AC impedance of a resistor is equal to its DC Resistance.
  • The AC circuit impedance for resistors is given the symbol Z.


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  • H

    Good Tutorial.

  • madhav bhattarai

    find the overall capacitance &individual voltage drops across two capacitor each with capacitance 470nF,&1microF respectively in series when they are connected to AC voltage.
    please !!!!!!!!!!!!provide me full answer step by step.

  • madhav bhattarai

    calculate the equivalent capacitance in series and parallel when three capacitors having capacitance 31F ,35F, 36F respectively.

  • P

    Can someone please tell me that how does a rheostat control the amount of current in a circuit?

  • w
    woodywood picker

    i learn a lot of things in this tutorial… thanks guys….

  • e
    eugene p. arriesgado

    this page is of great help to me,.now, i can study in my own time w/the help of this page even w/o going to electronics/vocational school….thanks a lot…

  • s

    i can design one circuit but how much of resistor value used i don’t no please tell me

  • k

    Today in my tutorial i got resistor basics very well and i want to review my knowledge of electronics as i worked for about 20 years as electronics technician and in coming days going to search another job as electronics technician.

  • P
    Philip Malmstedt

    I want to study about electronics. I want to purse my goal to become a technician in the future. I am a hearing-impared person and am 48 years old. I have not completely finished this courses in the colleges and not getting it successfully. I want to learn what the electronics work.

    • Wayne Storr

      Hello Philip, Everything you need to learn Electronics is right here. Good look with your studies.

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