3/19 week4 day2 New things: Electrical Force and charge.

Today, the first experiment we did is that the professor use a balloon rub the hair and put it near the wall, predict the result. We find that the ballon and the wall are sticking together. 

Then we use tht balloon will be rubbed with a silk cloth, then we find that it sticks to the glass wall again.
The results of these show that after the balloon was rubbed, it can produce charge. and becasue of thse charge, the balloon become sticky.

Then the professor askes us to definite the charge for a 7 year-old kid, what we say is on the photo.

Then we start another experiment about Interactions of Scotch Tape Strips. In the first video, two partners peel their tape off the table and bring the non-sticky side of the tape toward your partner's strip. We find that the two tapes push each other. and larger distance means waker interaction.

In this video, we place two strips of tape on the table sticky side down and label them "B" for bottom, and press another strip of tape on top of each of the B pieces; label these strips "T" for top. Pull each pair of strips off the table. Then pull the top and bottom strips apart. We find that the two T tapes are repell and the two B tapes are also repell , but when we put one T tape and one B tape together, they stick together.

in this photo, in A and B we describe what happen in the two videos. In C,  my observations are consistent with the hypothesis that there are two types of charges.
In D, hypothesis is false, charges can be conducted by plastic.

In the left of the photo, we can calculate the angle=sin^(-1)(X2/L)
In the right of the photo, we did the exerices in the lab manual. 

in this photo, we make a sketch of a graph of F and r. and use the equation:F=A*r^B and find B=-2, A=Gm1m2. In the second photo, we did the graph in logger pro and curve it .

 in this photo,we show the force's relationship worked on q1 and q2.

 in this photo, we use the equation: F=kq1q2/r^2 to find the force worked  by p1 on p2. 

in this photo, we put q1 q 2 q3 in a xy-axis. and use  F=kq1q2/r^2 to find the force on x-asix and y-asix  on P3 by p1 and p2 

in this photo, we did an experiment usng the equipment in the photo. And we give power in it, we find that the paper is all floating.

Then we put another equipment on it, we find it will rotate。

In this photo, we want to find the relationship between F1 which worked by eletrons and F2 which worked by earth. 


Conclusion:Today in class, we did many experiments that about charges caused by electrical forces that cause an object to either attract or repel. we use Coulomb's law  to measure the electrical force which is found to be greater than gravity.