<img src="https://d5nxst8fruw4z.cloudfront.net/atrk.gif?account=iA1Pi1a8Dy00ym" style="display:none" height="1" width="1" alt="" />
Skip Navigation


Electrons are the fundamental unit of charge.

Atoms Practice
Estimated5 minsto complete
Practice Electrostatics
This indicates how strong in your memory this concept is
Estimated5 minsto complete
Practice Now
Turn In

Opposite charges attract and like charges repulse. The electron (and proton) is the fundamental charge unit. The charge of an electron and proton is \begin{align*} 1.6 \times 10^{-19} \end{align*} C. One can determine the number of excess electrons (or protons if positive charge) by dividing the objects charge by the fundamental charge. Most objects are electrically neutral (equal numbers of electrons and protons) and that's why gravity dominates on a macro scale.

Key Equations

\begin{align*}q = Ne \text{ }\end{align*} Any object's charge is an integer multiple of an electron's charge.


If an object has +0.003 C of charge, how many excess protons does the object have?

\begin{align*}q = Ne \text{ }\end{align*} \begin{align*} 0.003 \text{C} = N \times 1.6 \times 10^{-19} \end{align*} N = \begin{align*} 1.875 \times 10^{16} \end{align*} ; protons


  1. After sliding your feet across the rug, you touch the sink faucet and get shocked. Explain what is happening.
  2. What is the net charge of the universe? Of your toaster?
  3. As you slide your feet along the carpet, you pick up a net charge of \begin{align*}+4 \;\mathrm{mC}\end{align*}. Which of the following is true?
    1. You have an excess of \begin{align*}2.5 \times 10^{16}\end{align*} electrons
    2. You have an excess of \begin{align*}2.5 \times 10^{19}\end{align*} electrons
    3. You have an excess of \begin{align*}2.5 \times 10^{16}\end{align*} protons
    4. You have an excess of \begin{align*}2.5 \times 10^{19}\end{align*} protons
  4. You rub a glass rod with a piece of fur. If the rod now has a charge of \begin{align*}-0.6\ \mu C\end{align*}, how many electrons have been added to the rod?
    1. \begin{align*}3.75 \times 10^{18}\end{align*}
    2. \begin{align*}3.75 \times 10^{12}\end{align*}
    3. \begin{align*}6000\end{align*}
    4. \begin{align*}6.00 \times 10^{12}\end{align*}
    5. Not enough information

Review (Answers)

  1. The net electric charge you collected from the rug gets discharged when you come in contact with the sink faucet.
  2. Neutral
  3. c
  4. b

Notes/Highlights Having trouble? Report an issue.

Color Highlighted Text Notes
Please to create your own Highlights / Notes
Show More

Image Attributions

Explore More

Sign in to explore more, including practice questions and solutions for Electrostatics.
Please wait...
Please wait...