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This text is meant to accompany class discussions. It is not everything there is to know about uniform circular motion. It is meant as a  prep for class. More detailed notes and examples are given in the class notes, presentations, and demonstrations (click here.)
Click for the questions that go with this reading

Electric Fields Due to Point Charges


Introduction video below.

This video can be seen on YouTube at


Every body that has a net charge radiates an electric field, called an e-field. These e-field are vectors. They have magnitude and direction. The magnitude is calculated from the equation below.
Variables defines

The direction of the field is simple to determine with a single, stationary, point charge in space. It is the direction a positive charge would travel. Another words the field points away from positive charges and towards negative charges.

If multiple charges are present then the DIRECTION of the e-field is determined by:

  • Finding the direction of the e-field due each point, (one at a time.)
  • Breaking up the e-field vectors into horizontal and vertical components.
  • Adding up these components to find the net e-field's horizontal and vertical component -like you have done previously with free body diagrams.
  • Make a solution triangle to calculate the e-field's magnitude and direction.


This video shows you how to find the net e-field due to 2 charges by finding each e-field's magnitude and direction followed by adding these up vectorially.

This video can be found on YouTube at

  • Question
  • Video Solution

Calculate the net electric field at the point in space shown below.

setup's image

Video of this solution on YouTube is here:

Well not yet. But soon. some point.
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by Tony Wayne ...(If you are a teacher, please feel free to use these resources in your teaching.)