Electrostatic Force
Coulomb's Law
Learning Objectives
 | Determine the electrostatic force between two charged objects at rest. |
| Calculate the electric force between the electron and proton of a hydrogen atom. |
Equipment
Coulomb's Law Apparatus, cotton cloth and clear strip, wool cloth and white strip.
Set-Up
| Align the pith ball hanging on the thread to the same height as the pith ball on the nylon tube in the wooden block. |
Procedure
1. This lab works best with a group of two students.
| Remove the sliding block from the tower. |
| Charge the white strip by rubbing with the wool cloth. |
| Charge the pith ball on the block by touching it with the white strip. Do this several times. |
| Return the wooden block into the tower. |
| Approach the hanging pith ball, and the two should attract, touch, and separate. |
2. After touching the two pith balls will have the same charge. Now start collecting data.
| Record the neutral position of the hanging pith ball before starting. Photo below: 4 cm is the starting position. |
| Move the block pith ball until the two balls are separated by 3.0 cm. Like the photo above. How far did hanging ball swing away? Record your observation in the Coulomb's Law Data Collection Tool on line 10 as a Force. |
| Move the block pith ball to the separation distances listed in Column B of the data tool. Record how far the hanging ball swings away. Photo below: 2.0 cm separation and the hanging ball has moved 0.75 cm away. |
| Graph your Part I results on graph paper, then compare to the Data Tool's first graph. |
3. Parts II of the Data Tool, use Coulomb's Law to calculate the force the horizontal ball exerted upon the hanging ball. Use the following:
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4. Part III use Coulomb's Law to calculate the electric force on the proton exerts on an electron in the Hydrogen atom. Use the following:
| Electron charge = -1.602 X 10-19 C |
| Proton charge = 1.602 X 10-19 C |
| Hydrogen atom radius = 0.53 X 10-10 m |
The Lab Report for the group is due at the next class.