Day 8: Electric Charge and Force

Balloon Demo

In the beginning of the class, the professor demonstrated a demo of balloon that is rubbed with the hair and put near the glass wall and we need to predict what would happened. Our predict is that it would stick to the wall.

The second condition is that the balloon is rubbed with silk cloth, the result would be the same even though rubbing with silk cloth would cause less negative charge than rubbing with hair.

What is A Charge?

Professor Mason asked us to come out with a definition of charge to a 7 year-old kid. The definition is in the photo.

Interactions of Scotch Tape Strips

The first experiment is when we took the non-sticky side of two strips of tape and put them close to each other, and the result was that they repelled each other.

In second experiment, we taped another tape called T on top of the original tape called tape B. And when we put tape B together, they repelled as well as when we put tape T together.

This is our observation and results of the experiment.

Electric Force Law Video Analysis 

We calculated the angle sin^(-1)(X2/L) and the force

These are the graphs for F vs. d. We fit the line with the equation F-A*r^B, where B = -2, and we find our A to be 1.45*10^-5

This is the force relationship between a positive charge and a negative charge.

We did the example problem to find the force by p1 and p2.

Demonstration of Stormball

These four photos are the predictions and the actual results when turning on the stormball machine under different conditions.

Example Problem

This is another problem which we need to find the relationship between F1 and F2.

Conclusion

Today in this class, we learned what a charge is by looking at the balloon sticking to the wall, tapes repelled each other, and the storm ball experiment. We also learned that how to calculation the force between 2 things.