UMDL 5B30.20 - Charge Distribution on Conductors

Assembly Operation Analysis See All Print

Operation Information

Overview
There are six variations of this demonstration:

Instructions
Uniform Distribution on a Sphere
Apply charge to a sphere with the piezo charger. Sample the sphere with the proof plane to measure charge on the electroscope. Discharge the electroscope and repeat sample. You will observe the same charge all over the sphere’s surface.

Equally Divide Charge onto a Nearby Sphere
Start with discharged spheres. Charge a sphere with the piezo charger. Bring the same-sized, discharged sphere into contact with the charged sphere. Sample either sphere with the proof plane and measure the charge on the electroscope. Discharge the electroscope and sample the other sphere. You will observe that the charge was evenly divided and that both spheres have the same charge.

Induced Charge on a Nearby Sphere
Start with discharged spheres. Charge a sphere with the piezo charger. Bring the same-sized, discharged sphere into proximity of the charged sphere. Ground the discharged sphere on the far side from the charged sphere with your finger (this works best if you are touching a ground with your other finger). Sample the charged sphere and measure on the electroscope. Sample the grounded sphere and measure on the charged electroscope. The charges should negate.

Absence of Charge on Cavity Surface of Hollow Sphere
Take the hollow sphere with the hole at the top, make sure it is discharged. Charge the sphere with the piezo charger. Sample the exterior of the sphere with the proof plane and measure on the electroscope. Discharge the electroscope. Sample the interior of the hollow sphere with the proof plane. Make noise inside the sphere, but be careful when removing the proof plane not to touch the exterior. Measure the inside charge on the electroscope, you will find that it has zero charge. You can repeat a charge measurement of the outside and will find that the charge is still there.

Non-uniform charge on a Teardrop
Take the discharged teardrop surface and apply charge with a piezo charger. Sample various points on the surface with the proof plane. You will find that the shorter radii of curvature produce higher charge regions than the longer radii of curvature.

Non-uniform charge on a Hot Dog
Take the discharged hotdog surface and apply charge with a piezo charger. Sample various points on the surface with the proof plane. You will find that the shorter radii of curvature produce higher charge regions than the longer radii of curvature.

Piezo Charger: When you squeeze the handle of the charger, a piezo crystal is squeezed and creates a potential. When you touch the tip to a surface it deposits a charge on that surface. It is best to place the charge quickly. You may need to deposit charge a number of times to accumulate sufficient charge to detect. To do this, charge the surface, ground the tip on the ground plate, then repeat the process.

Preview Time: 10

5B30.20 - Charge Distribution on Conductors

Objective: Show how charge distributes itself on a conductor.