INTRODUCTION

Relevance of the Topic

The study of types of electrification is of fundamental importance for the discipline of Physics, and is the basis of various phenomena and practical applications that we encounter in our daily lives.

Understanding the mechanisms by which objects can become electrified (gain or lose electrons), helps us to elucidate phenomena such as lightning, electrification by friction (rubbing balloons on fabric and sticking to hair) and even the operation of electronic devices. Moreover, this study is the foundation for understanding more advanced concepts in Physics, such as the movement of electric charges in an electromagnetic field.

Contextualization

This topic is located within the Electricity block in the mandatory Physics curriculum of the 2nd year of High School. It comes after the introduction to fundamental concepts of electricity, such as electric charge, electric force, and electric field, and serves as a connection to future topics, including conductors and insulators, electric potential, and electric current.

By understanding the types of electrification, students are enriching their understanding of how electricity works in practice. These fundamental concepts will also be present in later topics such as Gauss's Law and Ampere's Law, which are pillars in modern Physics and in more advanced disciplines, such as Engineering and Medical Physics. Therefore, mastering this content is essential for the progress of studies in related areas.

THEORETICAL DEVELOPMENT

Components

• Electrification by friction (or direct contact electrification): This is the first type of electrification we will discuss and the term is due to the fact that electrification occurs due to friction between two bodies. Each time an object is rubbed against another, electrons are transferred between them, producing a situation of static electricity. The amount of electrons that is transferred and the direction of the flow (whether from object 1 to object 2 or vice versa) depends on the properties of the materials involved.

• Indirect contact electrification (or induction): In this type of electrification, the body to be electrified does not come into direct contact with the already electrified body, but rather with a conductor that is in contact with the latter. This phenomenon is intrinsically linked to the concept of conductor and insulator, which we will see later.

• Electrification by electrostatic polarization induction (Corona Effect): The Corona Effect is a physical phenomenon that occurs when the air around a high voltage electricity conductor is ionized. The interaction between the ionized particles and the electric field produced by the conductor produces a state of electrification that can be either positive or negative.

Key Terms

• Electric Charge: A fundamental property of matter that quantifies the hypothesis of a fundamental electromagnetic interaction. It is the cause of electrostatic and electrodynamical phenomena.

• Electron: An elementary subatomic particle that has a negative electric charge. The transfer of electrons between atoms and/or molecules is responsible for electrification phenomena.

• Conductor: Material that allows the free movement of electric charges, due to the high mobility of its electrons.

• Insulator: Material that impedes or hinders the movement of electric charges, due to the low mobility of its electrons.

• Electric Field: Region of space where a test charge undergoes the action of an electric force.

Examples and Cases

• Electrification of an object by friction: A classic example of this phenomenon is when we rub a plastic straw with a piece of paper and then bring the straw close to small pieces of paper. The pieces of paper are attracted to the straw due to the electrification by friction and the interaction between the electric charges present in them.

• Indirect contact electrification: We can observe an example of this phenomenon when we bring a glass rod previously electrified (by friction with silk, for example) close to a neutral metal rod. The metal rod, which is a conductor, becomes electrified by induction, without there being direct contact between it and the glass rod.

• Corona Effect: This phenomenon is commonly observed around high voltage lines on rainy or foggy days. The ionization of the air around the transmission line cables leads to the formation of an electric field that can lead to the electrification of nearby objects.

DETAILED SUMMARY

Relevant Points

• Electrification by friction: It is the transfer of electric charge between two bodies that come into contact and subsequently separate. This is one of the basic mechanisms by which objects can be electrified, and involves the transfer of electrons.

  • Different materials have different affinities for electrons, resulting in a directional charge transfer. For example, when you rub a balloon on your hair, the balloon receives electrons from the hair, acquiring a negative charge. This extra charge allows the balloon to attract and "stick" small pieces of paper, which are neutral.

• Indirect contact electrification: This type of electrification occurs when a neutral object comes into contact with an electrified object, allowing electrons to flow between them. After the contact, the objects are separated and each acquires an electric charge.

  • It is important to note that, during the contact, there is an equalization of potentials between the two objects. In other words, the final goal is for both objects to have the same electric charge.

• Electrification by electrostatic polarization induction (Corona Effect): A less known form of electrification. The corona effect occurs in high voltage situations, where the air around a conductor is ionized, due to strong electric fields present. This ionization causes a current flow, leading to a charge transfer to nearby objects.

  • This phenomenon is crucial for understanding how electricity "jumps" between high voltage lines and the ground during the occurrence of lightning.

Conclusions

• Electrification is a natural phenomenon and understanding its mechanisms provides a solid foundation for understanding many other electrostatic processes.

• Although there are various electrification strategies, all of them are a variation of the same basic principle: the movement of electrons between the atoms or molecules of one substance to another.

• The direction of the electron flow, whether from object 1 to object 2 or vice versa, depends on the properties of the materials involved.

Exercises

1. Describe the process of electrification by friction, explaining how the transfer of electrons occurs and why the resulting charge can be positive or negative.

2. Suppose you have a positively charged glass rod by friction with silk. How could you use this rod to electrify a neutral object by indirect contact?

3. Explain what the Corona Effect is and give examples of situations where it can be observed in practice.