5A20.10 - Coulomb's Law
Demonstrate electrostatic forces between two charged spheres.
Place the columb assembly on one side of the table and clamp it down. Place the laser on the opposite side of the table and point it at the mirror that is attached to the tension wire. Make sure the placement of the sliding ball does not interfere with the laser dot projection on the wall from the mirror. Connect the aluminum plate to ground and include a piezoelectric squeezer for charging the spheres.
Initial adjustment requires that the separation between the spheres be set to zero and assure that the sliding and rotating ball guages also read zero. Adjust the magnetic brake of the rotating ball to center at zero. Adjust the laser to produce a spot on the wall above the students heads and mark the zero with a pointer of blue tape. After the demo is done being used, loosen the tension in the wire by loosening the screw at the base which holds the wire taut. This should not be left under tension when the demo is not in use.
Apply charge to both spheres, either same or opposite charge, using the included piezoelectric squeezer. It is important to assure that the spheres are charged equally or the results can be questionable. Equal charge can be produced by shorting (touching) the spheres together for same/equal charges, or for opposite charges, piezo tip on one sphere and your finger on the other. Immediately pull the sliding ball of charge far from the rotating ball. Let the rotating ball stabilize, note that it should come to rest where the zero spot on the wall is projected by the laser. Next, interpose the sliding charged ball into the area of the rotating ball by linear increments and note that the laser deflection on the wall follows the 1/r^2 relationship in Coulomb's Law.