• Electric field vector calculations

Pre-requisite skills:  Basic understanding of vector algebra and Coulomb's law.

Approximate completion time:  Under an hour.

Applet by Wolfgang Christian

Like Charges

1.  Select "Like charges" in the applet above. 

(a)  Where is the origin (the point where x and y are defined to be 0) in the above applet?

(b) The two large charges (each charge having Q = +4 mC) are separated by a distance d = 3.  Place the small green charge a distance h = 3 directly above the large charge on the right.   According to the applet, what is the strength of the force acting on the green charge at this point?

(c)  Assuming the readout on the applet is correct in part (b), calculate the charge on the green particle.  Show all work.

(d) Using your result from part (c), calculate the force acting on the green charge if it was placed at the point (x,y) = (1, 0.5).   Does this agree with the applet readout?

(e)  What force acts on the particle at a point midway between the two positively charged particles.  Why is this expected?

2.  If a charge is placed in an electric field and released, will it follow the electric field lines in its trajectory?   Explain.  (Hint:   Think about what happens once the charge has a velocity.)   Run the applet to test your answer.

Unlike charges

3.  When the two large objects are oppositely charged, how is your answer to Question 1(e) changed? Explain.

Helpful Resources

1. The Book of Phyz - Electrostatics by Dean Baird.
2. The Physics Hypertextbook by Glenn Elert
3. Electromagnetism Applets by Angel Franco Garcia (in Spanish).
4. Electric Field (Physics) by Sadahisa Kamikawa.
5. The Electric Force by Physics 2000
6. Electric and Magnetic Interactions:  The Movies by Ruth Chabay
7. Electric Fields by Angel Franco Garcia (in Spanish)
8. Electric Charges in Java by Sebastian Rodriguez.

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