Electrostatic Forces (8th Day)

Spring 2015
Professor Mason
March 19 class

Static with Balloon and Charge
Firstly in class, we learned about static that involves with a balloon. The first experiment was  to rub balloon on hair, then it sticks to the glass because it produces statics. The next experiment was to rub the balloon on silk, then sticks it to the glass; as a result, it sticks just for a while because there is no as much static as while rubbing on hair. Next, we needed to define charge for 7-years-old student; the example of charge is magnet: one side of the magnet can stick with the different side of the other magnet.













Electrostatic on Scotch Tape

In class, we did another experiment including electrostatic; however, this time we did it with scotch tape. First, we need 4 scotch tapes with approximately 10 cm long. First experiment: put a strip of scotch tape on the table with the sticky side down, then curl over the end of each tape to make a non-stick handle. Then, we peel the tape off the table and bring the non-sticky side of the tape toward another tape. As a result, the tape sticks to each other.
Second experiment: we place two strips of tape on the table sticky side down and we label them "B" for bottom. We press another strip of tape on top of each of the B pieces; then, we label these strips "T" for top. We pull each pair of strips off the table and we pull the top and bottom strips apart; then, we put one "T" strips of tape toward another tape. As a result, they're both attracted.

Next, we put one "B" strips of tape toward another tape, and the result was they move away from each other. The same result goes with the interaction between a "T" and a "B" strips.
The idea is that the interaction between objects that have been rubbed is due to a property of matter that we called it charge, which contains negative and positive charge. Charge moves readily on certain materials, known as conductors, and  not on insulators. In conclusion, metals are good conductors, while glass, rubber, and plastic tend to be insulators.




Forces between Two Balls

In class, we did an experiment of two balls moving toward another involving electrostatic force. We were supposed to do this experiment on Logger Pro and analyze it based on the video given from the professor. The free body diagram of forces of the balls give us an equation of [Fx = F- T sin(theta)], which will equal to [T = W/cos(theta)]. There is also an equation which involves gravitational force between two masses m1 and m2 separated by a distance r, and that leads to an equation of [F = G (m1 m2)/r^2]. The F vs r graph is shown on the picture attached.

 We can compare when the ball move away from each other with the mathematical formulation of coulomb's law, which is [Fe = K r12 (q1 q2)/r^2], which r12 is a unit vector from q2 to q1, r^2 is the square of the distance between the two charged objects in meters, K is a constant that equals to 9x10^9 Nm^2/C^2, and q is the charge in coulombs. We used this formula to define the two balls as charge in coulombs as they move away from each others.

The next experiment after we analyzed the balls' movement was to make a graph out of it by making an equation by using manual fit.

Electrostatic Experiment

 In class, we did another experiment involving electrostatic machine. Professor placed some strips of paper on the machine to show that the machine is producing electrostatic if the machine is turned on. The strips of paper sorts of hovering in the air when the machine is turned on because there is a static on the machine. If we placed our hands on the machine, it would produce a static noise. The next one is that the professor place a rods that spins when the machine is turned on because the machine produces statics and it is conducted to the metal rods, so it spins.