Electric Charges 04 - Electric Fields Practice




  • Test Charge: A mathematical construct-- a charge that does not exert any influence on surrounding particles but IS influenced by other electric fields.
  • Conductors - materials where electrons can roam
  • Insulators - materials that keep their electrons close to home
  • coulomb - a unit of electrical charge (see below)


  • e-mass = 9.1 x 10-31 kg
  • charge of an electron = 1.60 x 10-19 coulombs (C)
  • ke = 8.987 x 109 Nm2/C2


      1. Electrical Force: Fe = (keq1q2)/r2
      • Electrical Field: E = Fe / qo where qo  = a positive test charge
      1. #1 and #2 (above) work well together to tell us about the strength of the electrical field at some distance (r) away from a point source:

        E = (keq)/r2

        Please keep in mind that E is a vector and that we will frequently need to componentize 'r' in terms of unit vectors i and j


Let's get someone up to dissect the long, thin rod problem....


Here's a helpful review of efield vectors: physicsclassroom.com)

And THIS about efields

And THIS about particles in motion in an efield

Here is the PHET animation


We haven't covered near enough material for a FR problem on this material... also, much of what we've done is very, very similar to what we've done with forces.


Whatcha wanna do for tomorrow? Please converse using the somewhat controversial quote that comes to us from a former hotshot computer science student here at GHHS:

"Rubrics stifle creativity"Seth D.


Problems 5, 11, 21, 49 et al? (please choose one other problem that illustrates a skill or concept you think is helpful for your team to review.

Do that problem and then <somehow> share the results with your team sometime today. Oh and please keep the time-honored science concept of GOLDILOCKS front and center.

That is to say that the problem you select shouldn't be so easy it's irrelevant, or so hard that it is obscure... we want to benefit the entire team on this.