Electrostatic Forces

On September 18th, 2014, Mt. SAC's Physics 4B class was introduced to the topic of electromagnetism.

Electrostatic Forces:

Professor Mason began the class by rubbing a balloon with some animal fur. He asked us if the balloon would stick to a glass cabinet door. We concluded that the balloon would stick and it did. We also included a free-body diagram of the situation.

Next, he rubbed the balloon with a silk handkerchief and were asked the if the balloon would stay this time. We concluded that it would not but the balloon did actually stick to the glass window.

We were then asked to attempt to explain mass and charge to a seven-year-old. Below is our result.

Next, we looked closer at electrostatic forces by using four pieces of scotch tape. First, we were asked to put together two pieces straight from the dispenser on their non-sticky side. They repelled each other.

We then though the lab manual told us to keep the bottom strip of tape on the table and attempt to put together the two top strips on their non-sticky side. The two strips were attracted to us and not each other.

We then did it correctly and compared the two bottom strips together. They repelled each other whereas when the top and bottom strips were put together, they attracted.

Electric Force Law Video Analysis:

By using our knowledge from the previous semester of physics, we were told to find an equation to find theta. Our group came up with this equation:

And then, using the found equation, to find the force of the pull required when pulling back a child on a swing.

These are the equations that my group found and thought would be useful.

By using Logger Pro, we analyzed the video of a charged ball approaching a ball on a string.

This is our force by time graph.

And this is our Separation of Distance versus time graph.

We put together the Force, Separation of Distance, and the change of Distance versus time.

And this was our Electrical Force vs. Separation Distance graph. When we did the curve fit, however, we did not find our constant to be anywhere close to the accepted value. Somewhere, our equation for one of the graphs were wrong and when we fixed it, we found it to be .001% off from the accepted value.

This is our conclusion of the lab.

Coulomb's Law:

We were then told to find the charges of two particles with given information.

We were then told to draw vectors of two particles with the same directional charge.

Next, we were given some information and were told to find the force done on one particle.

And then, we were asked to recall information from the previous physics class to find the force of two particles in vector notation based on a graph.

Van de Graaff Generator and Storm Ball:

Next, Professor Mason demonstrated to us a Van de Graaff generator. This generator generated certain amounts of electrical energy, enough to raise the hairs of this wig.

And spin the Franklin motor. It spun because the electricity expelled through the curved outlets of the apparatus causing a force to push the apparatus.

It also slightly raised the streamers of this makeshift pom pom.

This is the inside of a Van de Graaff generator (the ball removed).

We were then asked to explain how this generator worked.

Next, Professor Mason showed us a Storm Ball. Unlike the Van de Graaff generator, this generator kept the electricity inside an insulated space and thus, no one was shocked.

We were then to find a ratio between the force and the radius of charge and gravity. It was found that the force of charge was much stronger than the force of gravity.