Static electricity/Howard Community College/fall2014/501 dancing balls
Team Members edit
Problem edit
- To get the original system set up and re-operational.
- Once operational, manipulate the contents of the box while it is functioning.
Conceive edit
Operate device normally, and then use a series or set of prods to manipulate contents.
Theory of Operation edit
Wimshurst Machine edit
A Wimshurst Machine is an electrostatic generator consists of two opposite rotating disks with several metal segments attached in equal spacing, metallic brushes, and a spark gap. The entire machine is usually connected to Leyden jars.
According to Wikipedia:
| “ | Any small charge on either of the two discs suffices to begin the charging process. Suppose, therefore, that the back disc has a small, net electrostatic charge. For concreteness, assume this charge is positive (red) and that the back disc ([A] lower chain) rotates counter-clockwise (right to left). As the charged sector (moving red square) rotates to the position of the brush ([Y] down arrow tip) next to front disc ([B] upper chain near center), it induces a polarization of charge on the conducting shaft ([Y-Y1] upper horizontal black line) holding the brush, attracting negative (green) charge to the near side ([Y] upper square becoming green), so that positive (red) charge accumulates on the far side (across the disc, 180 degrees away) ([Y1] upper square becoming red). The shaft's polarized charges attach to the nearest sectors on disc B, resulting in negative charge on B [Y] closer to the original positive charge on A, and positive charge on the opposite side of B [Y1]. After an additional 45° rotation, the positive (red) charge on A (lower chain) is repelled by a positive (red) charge approaching ([Z] near lower chain middle) a positive (red) charge on B ([Z] upper chain). The first collection comb ([Z] arrow-tipped lines to triangles) encountered allows both positive (red) charges to leave the sectors neutral (squares becoming black), and accumulate in the Leyden jar anode (red triangle) attracted to the Leyden jar cathode (green triangle). The charge completes the cycle across the discs when a spark (yellow zigzag) discharges the Leyden jar (red and green triangles).
As B rotates 90° clockwise (left to right), the charges that have been induced on it line up with the brushes next to disc A [X, X1]. Naturally the charges on B induce the opposite polarization of the A-brushes' shaft (viz., negative next to positive and positive next to negative), and the shaft's polarization is transferred to its disc. Disc B keeps rotating and its charges are accumulated by the nearest charge-collection combs. Disc A rotates 90° so that its charges line up with the brush of disc B [Y, Y1], where an opposite charge-polarization is induced on the B conducting shaft and the nearest sectors of B, similar to the description two paragraphs above. The process repeats, with each charge polarization on A inducing polarization on B, inducing polarization on A, etc. All of these induced positive and negative charges are collected by combs to charge the Leyden jars, electrical charge-storage devices similar to capacitors. The mechanical energy required to separate the opposing charges on the adjacent sectors provides the energy source for the electrical output. |
” |
What causes the balls to "dance" edit
The voltage created by the Wimshurst machine is conducted to the aluminum foil plates using copper wire. The voltage of the two aluminum plates are opposite charges. The charge of the bottom plate is transferred to the ball in the box and is then repelled, shooting upwards into the top plate. Since the top plate is an opposite charge, the contact between the ball and plate causes a discharge. The ball then falls back towards the bottom plate and the cycle is repeated.
Design edit
Box & Wiring edit
We decided to use the same box the previous group created, and wired it the same way.
Wimshurst Machine edit
We used two Wimshurst machines in this project:
- The small one (seen above)
- The large one:
Ultimately we opted to use the larger Wimshurst machine. The small machine lacked the proper bands for operation, using makeshift bands with rubber bands instead. This caused the machine to be less efficient than normal, and generated an insufficient amount of voltage. The larger one, although not self starting, output a sufficient amount of voltage.
To start the large machine, you must first rub a PVC pipe with a silk cloth and then transfer the static charge in the pipe to the machine. Afterwards, it functions as a normal Wimshurst machine. The reason why the large machine is not self starting is because the disks lack the metal sections, lacking a self-activated charge generator.