Electric Charge: Exploring the Basis of Electricity

Objectives

1. Understand the concept of electric charge.

2. Comprehend that electric charge can be both negative and positive, depending on the transfer of electrons.

3. Calculate the charge of a body based on the electric charge of an electron.

Contextualization

Electricity is a fundamental part of modern life. From lighting our homes to powering our electronic devices, electric charge plays a crucial role. Understanding what electric charge is and how it behaves is essential for grasping many of the phenomena we observe daily and for working in many technological and industrial fields. For example, by rubbing a balloon on a piece of wool, it acquires an electric charge that allows it to attract small pieces of paper. This simple phenomenon illustrates the basic principles of electrification, which are applied in various technologies, from electric motors to energy storage devices.

Relevance of the Theme

Understanding electric charge is fundamental in the current context, as electricity is one of the primary forms of energy used worldwide. Professionals who master these concepts are essential in sectors such as electrical engineering, telecommunications, industrial automation, and maintenance of medical equipment. Knowledge of electric charge is applied in the development of new technologies, improving industrial processes, and solving everyday problems, making it a valuable skill in the job market.

Definition of Electric Charge

Electric charge is a fundamental property of the particles that make up matter, and it manifests through the force of attraction or repulsion between these particles. There are two types of electric charge: positive and negative. Particles with like charges repel each other, while particles with opposite charges attract each other.

• The unit of measurement for electric charge in the International System is the coulomb (C).

• The electric charge of an electron is approximately -1.6 x 10^-19 coulombs.

• Electric charge is quantized, meaning it is always an integer multiple of the charge of an electron.

Transfer of Electric Charge

The transfer of electric charge occurs when a body gains or loses electrons. This process can occur in various ways, such as through friction, contact, or induction. Both electrons, which have a negative charge, and protons, which have a positive charge, are fundamental in electrification, but the transfer of electrons is what generally occurs.

• Electrification by friction: occurs when two different materials are rubbed together, resulting in the transfer of electrons from one material to another.

• Electrification by contact: occurs when an electrically charged material comes into contact with a neutral material, transferring part of its charge.

• Electrification by induction: occurs when an electrically charged material is brought close to a neutral material, causing a redistribution of charges in the neutral material without direct contact.

Calculation of the Charge of a Body

To calculate the total charge of a body, it is necessary to know the number of excess or deficit electrons it has. The total electric charge is obtained by multiplying the number of electrons by the charge of a single electron.

• The total electric charge (Q) is given by the formula Q = n * e, where 'n' is the number of electrons and 'e' is the charge of an electron (-1.6 x 10^-19 C).

• If a body has an excess of electrons, it will have a negative charge. If it has a deficit of electrons, it will have a positive charge.

• Understanding how to calculate electric charge is fundamental for solving problems in physics and electrical engineering.

Practical Applications

• Design of electronic circuits: engineers use the concept of electric charge to design circuits that control energy distribution in electronic devices.
• Maintenance of electronic equipment: electronics technicians need to understand the transfer of electric charge to diagnose and repair devices that use electricity.
• Development of batteries: scientists and engineers develop new energy storage technologies, such as batteries, based on the manipulation and transfer of electric charges.

Key Terms

• Electric Charge: property of particles that causes forces of attraction or repulsion between them.

• Coulomb: unit of measurement of electric charge in the International System.

• Electrification: process of transferring electric charge between bodies.

• Electrification by Friction: transfer of electrons between different materials through friction.

• Electrification by Contact: transfer of electric charge through direct contact between bodies.

• Electrification by Induction: redistribution of electric charges in a body due to the approach of a charged body, without direct contact.

Questions

• How can understanding electric charge impact the development of new technologies?

• In what ways do electricity and the transfer of electric charges influence your daily life?

• What is the importance of electricity and knowledge about electric charge in your future professional career?

Conclusion

To Reflect

Understanding electric charge is essential not only for physics but for countless technological and industrial applications. Electricity permeates our daily lives, from the devices we use to the infrastructure that supports our cities. Reflecting on the concepts of electric charge allows us to appreciate the complexity of electrical phenomena and the importance of mastering this knowledge to innovate and solve practical problems. Skilled professionals in this field are crucial for the development and maintenance of technologies that utilize electricity, reinforcing the strategic value of this knowledge in the job market.

Mini Challenge - Detecting Electric Charge with a Homemade Electroscope

Use a simple electroscope to detect and measure the electric charge of different materials.

• Gather materials: a glass jar with a lid, aluminum foil, a copper rod (or another conductive metal), thin copper wire, adhesive tape, scissors, plastic objects (like rulers), and pieces of wool.
• Build the electroscope following the instructions discussed in class.
• Charge a plastic object electrically by rubbing it against a piece of wool.
• Bring the charged object close to the top end of the copper rod of the electroscope and observe the behavior of the aluminum foil strips.
• Record your observations about how the aluminum strips move in response to the electric charge of the object.
• Experiment with different materials and methods of electrification (friction, contact, and induction) and document the results.
• Compare your observations with the theoretical concepts discussed in class and write a brief report on your conclusions.