Electric Charge 3/17/2014

Today, we were finally introduced to electric charges.  We started with rubbing balloons on the professor's fury head to charge up the electric charges... As a result, the balloons were able to stick to glass.  We then did the same but this time, we approach the charged balloon to confettis (punched holes).  We see the confettis first were attracted but quickly bounced off the balloon.

    

The charged balloon introduces a charge separation on the glass surface due to realignment of molecules...

 Rubbing against silk or fur produces electric charges that attract or repell the little punched out holes.

Based on this "invisible" interaction between charged objects, we concluded that there is an electric force acting upon them.  Our first experiment was conducted using electrostatic forces between two pieces of scotch tapes.  We first taped two strips of scotch tape onto the table then quickly peeled the tape off to bring the non-sticky sides of the tape toward each other.  They ended up repelling.  We then did the same sticking two strips of tape on the table and overlap tapping another two strips of tape onto each of the strips.  The results are answered as follows:

 The distance between the tapes directly affect the interaction between them...

Saxon demonstrating the attractiveness and repulsiveness between two +/+ and +/- charged tapes

Using some and measuring values....

In our second experiment, we did the Electric Force Law Video Analysis Activity.  Before we began our actual analysis, we first derived the expression for the electric force acting on a hanging ball by using the free body diagram for the ball being suspended at an angle and simple trigonometry to come up with a way of calculating angle REMEMBER 4A??  Finally, the derivation can be seen here:

We then had to do the actual video analysis....

Plotting a graph of Electric Force vs. Separation Distance with Logger Pro

Logger pro was used to determine the repulsion force verses the distance in the movie of a charged ball being pushed toward another like charge ball.  Above graph show that the force of the electrical repulsion is inversely proportional to the square of the distance.

Finally, we show that Coulombs law demos the inverse relationship between the force and the distance we saw in the Logger Pro graph.