# Measuring Static Electricity: A Classroom Investigation to Understand the Triboelectric Series

## Article excerpt

Static electricity results from a charge that transferred between two objects by touching the two objects together. The process of transferring charges by touching the two objects is known as triboelectric charging, with tribo referring to friction. Although every student has experienced static electricity, few understand how and why it happens.

Atoms have the same number of positively charged protons and negatively charged electrons, resulting in a neutral charge. Electrons can be transferred to other atoms, resulting in ions with an overall charge. Some atoms tend to lose electrons more easily and obtain a positive charge, whereas other atoms tend to gain electrons to obtain a negative charge. While subatomic structures are not discussed in depth until later grades, students should know about the forces between positive and negative charges.

A balloon rubbed on human hair gains electrons from the hair, resulting in a negatively charged balloon and many positively charged hairs. When the balloon and hair are separated, their opposing charges make them attract each other so that the hair stands up toward the balloon. Conversely, the positively charged strands of hair repel each other, resulting in the familiar halo of hair as the hairs try to avoid contact with each other. When the opposite mechanism happens and a charged material quickly transfers electrons to become neutral again, an electric shock is experienced.

Different pairs of materials rubbed together will transfer different amounts of charge. In order to characterize the differences between pairs of materials, scientists developed the triboelectric series, a list of objects ordered by how likely they are to become positively or negatively charged. The farther apart two objects are on this chart, the larger the amount of charge transfer that results when they touch. Thus, a triboelectric series can help a scientist figure out which pairs of objects will create a static-electric charge when they touch each other. Discovering this series through a classroom investigation helps students answer questions such as, "Does a wool sweater have more static than a cotton one? How can you tell?"

The lesson described in this article is a structured inquiry during which students quantitatively measure the amount of charge transferred between two different materials. If students are familiar with inquiry activities, the teacher may allow the lesson to be more student-centered by providing less support. Suggestions are provided in the text.

Accessing students' prior knowledge is vital to determining how much teaching needs to be done prior to the investigation. Students may have some misconceptions about static electricity and how it is different from magnetism (Nabb and Henry 2009). Giving a pre-assessment on static electricity a few days before the lesson helps the teacher prepare for activities and plan discussions to dispel these misconceptions. A suggested pre-assessment, which can be modified as needed, is found with the lesson plan on the project website (see Resources).

At the beginning of the lesson, students are asked to begin a KWL (Know-Wonder-Learned) chart on what they think they know about static electricity. As a prompt, prior to completing the KWL, students are shown a video of children playing on a trampoline and a girl's hair responding comically as the static raises her hair. Then the teacher elicits student suggestions about why the girl's hair stands up and how this phenomenon works, as students fill in the K portion of their chart. Engaging students in discussions about their own shocking experiences (e.g., sweaters and hair on a cold day, touching a doorknob and receiving a spark) or using a demonstration or activity using transparent tape to address the charge nature of static, as described in Nabb and Henry (2009), can address misconceptions before the investigation begins.

Classroom investigation

Safety note: Students should wear goggles during this investigation. …

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