- PK – grade 3 students
Students at this age should know that there are three types of matter: solids, liquids, and gases. They should also know that energy can be carried from one place to another by waves and by an electric current. Electricity (a form of energy) runs from the center of the plate and globe outward to the edge of the plate and the surface of the globe. If a fluorescent light or neon bulb are placed close to the plate or globe, electricity can flow through the lamp and through your hand. The amount of electricity that flows is tiny and you do not get a shock from it. A Van de Graaff generator can also be used to produce electricity that can flow from the generator and to the light bulb to turn it on.
- Grade 4 – 6 students
In addition to the content in the previous section, students at this grade level know that electrical energy can be converted to heat, light, and motion. When electricity flows through the plate or globe, the electrical energy is converted to light in the form of plasma which we can see with our eyes. Plasma is a fourth type of matter that results from excited gases. The moving parts in a Van de Graaff generator creates static electricity that can be used to light a neon or fluorescent bulb.
- Middle School students
Figure 3: Van de Graaff Generator
A Van de Graaff generator demonstrates how static electricity works. Static electricity can be explained by knowing that everything is made of atoms. Atoms consist of protons, neutrons and electrons. When static electricity is displayed, it is presenting the charge of electrons repeling one another. The Van de Graaff generator uses a moving belt to accumulate electric charge on a hollow metal globe on the top of an insulated column, creating a very high electric potentials. The generator can produce high voltage current at low current levels. A Van de Graaff generator can reach a 5 megavolt potential difference. Enough energy can be stored to produce a visible spark. When you hold a light bulb near the generator, the electricity can flow from the generator to the light bulb and produce light in the bulb, showing that electrons can move freely. You can also use a lumin disk to produce different waves and colors. A lumin disk is a clear glass, which is filled with multiple noble gases and has an electrode in the center. Once the electrons flow from the generator, it can produce different waves and colors.
- College level description
There are two important aspects of electricity: voltage and current. Voltage is the force which causes electrons to flow through a circuit and it is measured in volts (V). Current is a measure of the number of electrons that flow through a circuit and it is measured in amperes (A). The power outlets in our home have a very high voltage (120 V) and a high current (2 – 20 A) and getting a shock from a power outlet can be extremely dangerous. In contrast, the electricity that is generated by the plasma globe/ plate has a very high voltage (1000 – 10,000 V) but the current is very small. As a result of the low current, you do not get a shock when you hold a fluorescent or neon bulb near a plasma globe or plate. The electricity travels from the globe/ plate, through the bulb and through your hand to the ground. The closer you hold the lamp to the globe/ plate, the brighter the neon or fluorescent lamp should glow. The Van de Graaff generator can be challenging to get to work if the humidity is too high. Since the Science Carnival is outdoors and at night, a Van de Graaff generator is unlikely to work.
A neon bulb contains neon gas which is one of the noble gases on the furthest right column of the periodic table. Neon signs also contain neon gas inside a glass tube. When electricity flows through neon gas, an orange color of light is given off as a result of the electricity exciting neon molecules which, in turn, give off light of the color orange. You also can see neon gas being excited in the Colorful Gases activity.