Day 8 Electrostatic Forces

Electrostatic force was demonstrated by Prof.Mason using balloons. He would wipe them with animal cloth and give it a charge. Then asked us if it would stick onto glass. We said it would and it did. Prof. Mason then asked us to to draw a FBD of the balloon stuck on the glass.

We draw the FBD. Friction is up, mg is down. normal is perpendicular to the glass and the Fe is inward to the glass.

We then drew the charge distribution on white board representing the balloon.

Plus charges on the side of the glass, negative on the other side of the balloon.

We then did some tape experiment to find if there were more then two types of charges. The answer is that there is only two types. Positive and Negative. We used tape and scrubbed it in till one was positive and the other was negative.  Similar charges would repel, and different charges would make the type attract. Unfortunately we do not have the video or pictures of this part of the lab. :(

We then had a Active physics lab. We had to find the force the charge would repeal the ball.

We found Tension and the change of theta. F = mgtan(arcsin(dx/L)

We then used Logger pro to analyze the video. We found two fit equation for the data  from Logger Pro.

We fitted the equation to be F =AR^-2. Where A is a constant and R is radius. A = 0.1421.

The second fit equation, A = .1204 B = -1.934.

We then got those numbers and plugged them into Coulombs' Law. We showed that the force was portional to the square  of distance becuase of the way the graph looked. We also found q, and our percent error.

q = 1.56 * 10^-15C. The percent error was 3.3%. And the graph plotted showed a 1/r^2 similarity.

The last part of the lab was how charges interact with one another. We applied Coulombs' Law.

Some work was erased. But we found the F = -13.5*10^-6 N and the r vectors <-4.26*10^-6 N, -12.80*10^-6 N>.

Prof. Mason then did some demonstration with Van de Graaf Generator. To show the power of electrostatice force. Unfornuatley the video and pictures are missing.

Prof. Mason then demonstrated the Lighting Ball sphere. Again the video and pictures are missing.

We did some Active Physics problem to relate electric and charges in different situations.

White board work, we found K to 8.99*10^9. We divided Fg/Fe

We found Fe = 4.2*10^42. Much much much bigger then Fg.

Summary:
We talked about electrostatic force, had an example of the balloons sticking the the glass. Drew a FBD of the balloon.
Found an expression for F for the Active Physics lab. Plotted how the chrage ball would displace the other. Fitted equations that would find the constants A and B. Found that the experiments follows the behavior of 1/r^2. Our error for the experiment was 3.3%. Found the q to be 1.56*10^-15 C. Found the F to be -13.5*10^-6 N. And the r vectors <-4.26*10^-6 N, -12.80*10^-6 N>.
Then Prof. Mason Demonstrated  Van de Graaf Generator and the Lighting Ball Sphere. Pictures and Video missing. :(
We then lastly worked out how Fg compared to Fe. Fe is much much much bigger than Fg.
Fe = 4.2*10^42.