Hidden Charges

Overview

Here you will explore the electric field produced by a number of charged lines and extended objects (cylinders, prisms, etc.). However, you can't see the charged objects.

The program displays a rectangular area that contains some hidden charges. The situation looks something like this:

although the charges are not in the same locations. The green box is a one-unit high Gaussian surface.

The program draws a field arrow at the mouse pointer's position (just like last time). But there are two (or maybe three) more things you can do here:

  1. Click the right button to draw a field line. The color along the line indicates the strength of the field; red is strong, and blue is weak.
  2. Shift-control-alt-left click to drop a field arrow.
  3. Draw a (green) surface for Gauss's law:
  4. The applet calculates and prints the amount of charge within the surface. Click the left button again to clear the integral.
  5. Hit "E" (for "erase"), Backspace, or Delete to clear the lines and laws.
(Confused)

Questions

How many charged objects are in the rectangular area?

Give the coordinates, magnitudes and signs of all the hidden charges. For a charge that is not a point charge, give the coordinates of the approximate center of the distributed charge. The coordinates of the point where the cursor is located appear in the browser's status line at the bottom of the window. If you manage to put the cursor directly on a line charge, the arrow will disappear, and a small circle will appear there.

Indicate which charges are point charges and which are spread over some finite area.

For each of the non-point charges, indicate the shape of the charge distribution. Is it square, circular, or something else?

At how many points in the area is the electric field equal to zero?

Give the coordinates of those points where E = 0.


When you have finished here, try some practice questions.


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