Lectures on Physics has been derived from Benjamin Crowell's Light and Matter series of free introductory textbooks on physics. See the editorial for more information....

Electric and Magnetic Forces

In this exercise, you are going to investigate the forces that can occur among the following objects:

nails

magnets

small bits of paper

specially prepared pieces of scotch tape: Take a piece of scotch tape, bend one end over to form a handle that won't stick to your hand, and stick it on a desk. Make a handle on a second piece, and lay it right on top of the first one. Now pull the two pieces off the desk and separate them.

1. Do the forces get weaker with distance? Do they have some maximum range? Is there some range at which they abruptly cut off?

2. Can the forces be blocked or shielded against by putting your hand or your calculator in the way? Try this with both electric and magnetic forces, and with both repulsion and attraction.

3. Are the forces among these objects gravitational?

4. Of the many forces that can be observed between different pairs of objects, is there any natural way to classify them into general types of forces?

5. Do the forces obey Newton's third law?

6. Do ordinary materials like wood or paper participate in these forces?

Last Update: 2009-06-21