Question

When a glass rod is rubbed with a polyester scarf, the rod becomes a) negatively charged. b) positively charged. c) neutral. d) either negatively charged or positively charged, depending on whether the scarf is always moved in the same direction or is moved back and forth.

Short answer

Question: After rubbing a glass rod with a polyester scarf, the charge on the glass rod is ___________. a) negatively charged. b) positively charged. c) neutral. d) impossible to determine.

Step-by-step solution

Identify the objects involved in triboelectric charging

In this problem, the two objects involved are a glass rod and a polyester scarf.

Consult the triboelectric series

The triboelectric series is a list that ranks materials according to their tendency to gain or lose electrons. When two materials are rubbed together, the one higher in the series will likely become positively charged (losing electrons) and the one lower in the series will likely become negatively charged (gaining electrons). In this case, we consider the materials involved - glass and polyester.

Determine which material gains or loses electrons

Based on the triboelectric series, glass has a stronger tendency to lose electrons compared to polyester. This means that when glass is rubbed with polyester, glass will lose electrons and polyester will gain electrons.

Determine the charge on the glass rod

Since the glass rod loses electrons, it will become positively charged. Thus, the correct answer is: b) positively charged.

Key concepts

Triboelectric Series

When two different materials come into contact, and then are separated, the phenomenon of triboelectric charging occurs, where one material becomes electrically charged at the expense of the other. The triboelectric series is a helpful guide that predicts which material will gain or lose electrons based on their relative position in the series.

The series lists materials in order of their tendency to become positively or negatively charged. Materials at the top of the series are more likely to lose electrons and thus acquire a positive charge, while those at the bottom are more likely to gain electrons, becoming negatively charged. For example, glass tends to be higher up on the series than polyester, indicating that when these two materials are rubbed together, the glass is more likely to lose electrons and become positively charged.

Importance of the Triboelectric Series

The series is crucial for predicting the outcome of triboelectric charging in various real-world scenarios, from industrial processes to everyday static electricity observations. Understanding this series can help in designing materials and objects that minimize unwanted static charge buildup.

Electric Charge

Electric charge is a fundamental property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of charges: positive and negative. Like charges repel each other, while unlike charges attract. The presence of an electric charge can be felt by the force it exerts on other charged objects or by a movement of charges in response to electric fields.

When materials are rubbed together, charges can be transferred between them, resulting in one object becoming positively charged and the other negatively charged. This is due to the imbalance of electrons, which carry a negative charge. The overall principle of conservation of charge states that the total electric charge in an isolated system remains constant. Thus, when one material loses electrons and becomes positively charged, another material gains those electrons and becomes negatively charged.

Conservation of Charge

The rule that the total charge is conserved during any process is pivotal in understanding electric phenomena. Even when electrons are transferred between objects in triboelectric charging, the total number of electrons remains the same; they are merely redistributed.

Electron Transfer

Electron transfer is the process where electrons move from one atom or molecule to another. It is a fundamental aspect of chemistry and physics, underlying a range of phenomena, including electricity, chemical reactions, and biological processes.

In the context of triboelectric charging, electron transfer occurs when two materials are rubbed together. Electrons, which are the negatively charged particles orbiting an atom's nucleus, are transferred from the material that is less inclined to hold onto them to the one with a stronger affinity for electrons. This transfer of electrons is what leads to one of the materials becoming negatively charged, while the other becomes positively charged.

Role in Triboelectric Charging

Electron transfer is a cornerstone for explaining how objects get charged through friction. Knowledge of electron transfer mechanisms is not only crucial for understanding triboelectric charging but also important for the study of electrical conduction and the design of electronic devices.