What Causes Lightning?
Lightning is a powerful display of static electricity in nature. But what is static electricity? In this lesson, students will learn about static electricity and electric fields by building a device that can detect electrical charges, called an electroscope. They will use their electroscope to investigate how well different materials can build up electric charges by rubbing them against wool. During their experiments, students will be able to demonstrate how electric fields exert forces on objects close by.
- Explain static electricity and what it means when an object is charged.
- Demonstrate how objects can be charged by the triboelectric effect.
- Know that electric charges (or electrically charged materials) create an electric field around them; this means they can push or pull on nearby objects without touching them.
- Carry out an investigation to demonstrate static electricity using an electroscope.
- Explain how an electroscope works.
- Know that some materials acquire static electricity more easily than others.
- Describe the connection between static electricity and lightning.
- 12 inches of uncoated brass or copper wire (about 16 gauge)
- Drinking glass or glass jar
- Cardboard to cover the opening of the glass or jar
- Tape or poster tack
- Latex balloon. Avoid other balloon materials such as Mylar or Vinyl.
- Wool yarn, wool cloth, or wool felt to rub the objects with
- Other test objects:
- Print out a worksheet for each student.
- Select additional materials you want the students to test. Possible materials are wood, other plastic objects, glass, or rubber.
- If you bought a spool of copper or brass wire, cut the wire into 12-inch pieces. One piece for each student group.
- Note: This experiment works best in a dry environment. If it is too humid, the experiment won't work as well. Humidity in the air makes the air more conductive and able to absorb excess charges. As a result, objects won't hold static charges well in a humid environment. An ideal relative humidity for electrostatic buildup is below 40 percent. Between 40 and 60 percent, a charge buildup is still possible but at a significantly reduced level.