Skip to main content
Chemistry LibreTexts

11.8: Resistors

  • Page ID
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

    \( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)

    ( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)

    \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

    \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)

    \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

    \( \newcommand{\Span}{\mathrm{span}}\)

    \( \newcommand{\id}{\mathrm{id}}\)

    \( \newcommand{\Span}{\mathrm{span}}\)

    \( \newcommand{\kernel}{\mathrm{null}\,}\)

    \( \newcommand{\range}{\mathrm{range}\,}\)

    \( \newcommand{\RealPart}{\mathrm{Re}}\)

    \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

    \( \newcommand{\Argument}{\mathrm{Arg}}\)

    \( \newcommand{\norm}[1]{\| #1 \|}\)

    \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

    \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    \( \newcommand{\vectorA}[1]{\vec{#1}}      % arrow\)

    \( \newcommand{\vectorAt}[1]{\vec{\text{#1}}}      % arrow\)

    \( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vectorC}[1]{\textbf{#1}} \)

    \( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)

    \( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)

    \( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

    \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)


    • Function as a load
      • convert electric energy to heat
      • P = IV = rate of energy consumption
      • Used in resistance heaters
      • Used to control current
      • Do Not Overload!
    clipboard_e961b93c94c5b1f5c3675a9a2d9b82eab.pngFigure \(\PageIndex{1}\): Common resistors. (David Ludovino, CC 3.0, Wikimedia commons)

    What happens when to much current passes through a resistor?

    Video \(\PageIndex{1}\): 2:48 min YouTube by Tariq Lab showing what happens if you send too much current through a resistor by hooking it up to too high a voltage (

    Resistor Values

    Use bands to describe resistors.  There are four types of bands

    1. Digits
    2. Multiplier
    3. Tolerance
    4. Temperature Coefficient
    Figure \(\PageIndex{2}\): Resistor Color Chart (4,5 & 6 band). (Koudstall; Open clipart, CC 1.0 )


    Variable Resistors

    There are two basic types of variable resistors, Rheostats and Potentiometers. Rheostats control current and potentiometers can control voltage or current.

    clipboard_ebd5110759781ad58a16aeb69aeeeaf21.pngFigure \(\PageIndex{3}\): Circuit diagram symbols for Rheostat and Potentiometer. (Belford, CC 0.0)


    Video \(\PageIndex{2}\): 1:18 min YouTube by Calco Tech Tips on the Difference Between Potentiometers and Rheostats (


    A Rheostat has two terminals and is used to regulate current and can be used for high current applications.

    Video \(\PageIndex{3}\): 4:35 min YouTube by DERF Electronics on How a Rheostat works - Step by Step & its different applications (, This video comes from their tutorial on An Overview on Rheostats.


    A potentiometer has three terminals can be used to regulate either current or voltage, but is not designed for high current flows.  Potentiometers are often integrated into circuit boards. They are effectively adjustable voltage dividers

    clipboard_e3d1145f7d4e9b4c564c0de648462b4d4.pngFigure \(\PageIndex{4}\): Copy and Paste Caption here. (Copyright; author via source)

    Here the potentiostat can be used to trigger an alarm if a gas concentration reaches a set concentration by adjusting the voltage at which a digital signal is sent.


    Video \(\PageIndex{4}\) 1:54 min YouTube on Potentiometers by Mouser Electronics  (


    The circuit on the left is a voltage divider and on the right is a potentiostat (variable voltage divider).  If you hoover over the power supply you will see it is 10 V, and when the simulation loads both circuits have 10K on either side of the divider.  Now if you move the resistance on the left side with the slider in the panel, you can see how the potentiometer can alter the current at the divider





    This page titled 11.8: Resistors is shared under a not declared license and was authored, remixed, and/or curated by Robert Belford.

    • Was this article helpful?