Physics Lab 12-Electrostatics
Materials: Styrofoam cups Styrofoam plates PVC Pipe Fur Scotch Tape
You will be investigating charging object by friction. When you are asked to write your observations, please do so in a clear, complete manner.
1. Tape a piece of string to a Styrofoam cup and hang it from the edge of the desk so that it can move freely. Rub the outside of the cup with fur. Rub a PVC pipe with fur and bring it near the hanging cup. A. Observations: Cup is repelled B. How does the distance between the PVC Pipe and the cup affect the results you observe?
The closer the objects are, the more the cup is repelled.
2. Take the PVC pipe and rub it with fur. Bring the fur near the suspended cup. A. Observations: Cup is attracted. B. What might you conclude with your observations?
The cup and the fur have opposite charges.
3. The forces between charged objects are called electric forces. When a charged object is brought close to the hanging cup, the cup is acted on by three forces: gravitational force pulling down, the string tension pulling up along the string, and the electric force.
A. Can you keep the hanging cup in a stable position with a single charged cup or PVC? B. Can you keep the hanging cup in a stable position with two or more objects? C. Sketch force diagrams showing all of the forces acting on the hanging cup for at least two different situations.
4. Hang two cups next to each other and see what happens?
Repel each other.
5. Bring the PVC pipe near the hairs on your arm. What happens?
The hairs stand up.
6. Charge two plates with fur. Try floating one on top of another. Can this work? Why or why not? Explain.
The top plate floats a little bit; the weight of the plate is too much for the electrostatic force.
7. Take approximately 15 cm of scotch tape and hang it from the desk so that it isn’t clinging to anything and it is free to swing. Rub the PVC Pipe