THe behavior of Insulators

           

Presenter: Tony Wayne, Albemarle High School, twayne@albemarle.org

                       

Va. SOL:

PH.13    The student will investigate and understand how to diagram and construct basic electrical circuits and …

 

National Standards:

In some materials, such as metals, electrons flow easily, whereas in insulating materials such as glass they can hardly flow at all.

 

Topic/Concept

Insulators and charge behavior

 

Materials

Š      Light string

Š      2 Rubber balloons

Š      Wool or rabbit fur

Š      Permanent, fat tip, black ink marker

 

Safety Considerations

            None.

 

AppleMark
Presentation

 

Inflate both balloons. Tie a string about 1 meter long on balloon. Draw a circle on the balloon. The circle should be about 6 inches or 15 cm in diameter. Draw a negative sign in the circle. Secure the loose end of the string to the ceiling. Using the wool or rabbit fur, carefully rub the negative sign and the circle. Take care not to rub or touch any other part of the balloon.

 

Charge up the second balloon with the wool or rabbit fur by rubbing the ENTIRE balloon. Hold this balloon close to the hanging balloon. The hanging balloon will be repelled and rotate such that the negative sign will point away from the charged balloon.

 

How the physics is demonstrated

 

The rubber balloons are insulators. When they are rubber by the wool or fur, they gain a net negative charge ONLY WHERE they are rubbed. This is because insulators do not allow the transfer or migration of charges. The hanging balloon’s drawn circle is the only part of the balloon that is carrying a charge. That is why it always aligns itself to be as far away from the other charged balloon as possible.

 

Construction  and Tips Regarding the Demonstration

 

None.

 

 

Sources & References

None.