2.0 Unit 2 Overview: Conductors, Capacitors, Dielectrics 

In Unit 2, we will be exploring the concepts of conductors, capacitors, and dielectrics. Conductors are materials that allow electric current to flow through them with relatively low resistance, while capacitors are electronic components that store electrical energy in an electric field. Dielectrics are insulating materials that can be placed between the plates of a capacitor to increase its capacitance.

We will discuss the properties of conductors, including their electrical conductivity and the factors that affect it, as well as their applications in electronic devices and power transmission systems. We will also examine the different types of capacitors and their uses, as well as the properties of dielectric materials and their role in electrical insulation and capacitor construction.

Key Terms

• Conductivity: The ability of a material to conduct electricity.
• Capacitance: The ability of a capacitor to store electrical charge.
• Insulator: A material that does not conduct electricity and is used to insulate conductors from each other.
• Dielectric constant: The measure of a material's ability to store electrical energy in an electric field.
• Electrical field: The region around a charged object where the electric force can be detected.
• Conduction band: The energy level in a material where electrons can move freely and conduct electricity.
• Coulomb's law: A fundamental law of electromagnetism that describes the relationship between electric charges and the electric force between them.
• Breakdown voltage: The voltage at which a material breaks down and conducts electricity, usually leading to electrical arcing or sparking.
• Polarization: The alignment of electric dipoles in a material in response to an external electric field.
• Resistance: The opposition of a material to the flow of electrical current.

2.1 Conductors 

Conductors are materials that allow electric current to flow through them with relatively low resistance. They are materials with many free electrons that are able to move easily in response to an electric field, allowing for the flow of electric charge. Common examples of conductors include metals such as copper, aluminum, and gold, as well as some non-metallic materials such as graphite and plasma.

The ability of a material to conduct electricity is determined by its electrical conductivity, which is a measure of the material's ability to conduct electric current. This property is affected by a number of factors, such as the material's atomic structure, temperature, and impurities or defects in the material. In general, materials with high electrical conductivity are considered good conductors, while those with low electrical conductivity are known as insulators.

Conductors are essential components in many electrical devices, including wires, cables, and circuit boards. They are also used in many other applications, such as in electrical power transmission and in the construction of electronic devices like smartphones, computers, and other electronic equipment.

2.2 Capacitors 

A capacitor is an electronic component that stores electrical energy in an electric field. It consists of two conducting plates separated by an insulating material, known as a dielectric. When a voltage is applied to the plates, charge accumulates on the plates, causing an electric field to form between them. The magnitude of the charge and the resulting electric field depend on the voltage applied and the capacitance of the capacitor, which is a measure of its ability to store charge.

Capacitors are used in a variety of electronic devices and applications. They can be used to smooth out variations in voltage, to filter out unwanted frequencies in electronic signals, and to store electrical energy for short periods of time. They are also used in timing circuits, where they can be used to control the rate at which a circuit switches on and off.

Capacitors come in many different shapes and sizes, ranging from small ceramic capacitors used in electronic circuits to large capacitors used in electrical power transmission systems. They can be constructed using a variety of different materials, including ceramic, electrolytic, and film capacitors. The choice of capacitor depends on the specific application, as different types of capacitors have different characteristics and performance parameters.

2.3 Dielectrics

A dielectric is an electrical insulator that can be placed between the plates of a capacitor to increase its capacitance. The dielectric material is placed between the conductive plates and is used to separate them while allowing an electric field to form between them. When a voltage is applied across the plates of the capacitor, the dielectric reduces the electric field strength, which allows more charge to be stored on the plates and increases the capacitance.

Dielectrics are used in many different applications, including in capacitors, in electrical insulation, and in the manufacture of electronic devices. The choice of dielectric material depends on the specific application, as different materials have different properties and performance characteristics.

Common materials used as dielectrics include air, paper, mica, ceramic, and various types of plastics. Each material has its own unique properties, such as dielectric constant, breakdown voltage, and temperature stability, which affect its suitability for a particular application. Dielectric materials with high dielectric constants are often used to increase the capacitance of a capacitor, while materials with high breakdown voltages are used in high-voltage applications where electrical insulation is critical.

Dielectric materials are also important in the design and construction of electronic devices, where they are used to insulate conductive components and to prevent electrical interference. Dielectric materials are selected based on their ability to provide high-quality insulation, resistance to environmental factors like moisture and heat, and compatibility with other materials used in the device.

Questions for Review

• What is the difference between a conductor and an insulator?
• How do conductors and dielectrics differ in terms of their electrical properties?
• What are some common applications of capacitors in electronic circuits?
• How does the dielectric constant of a material affect its suitability for use as a capacitor dielectric?
• Why are metals like copper and aluminum commonly used as conductors in electrical wiring and electronics?
• How does the thickness of a dielectric material affect the capacitance of a capacitor?
• What is the role of a dielectric in a capacitor, and how does it affect the capacitance of the capacitor?
• What are some examples of non-metallic conductors, and how do they differ from metallic conductors?
• What is the difference between a polar and a non-polar dielectric, and how does this affect their performance in a capacitor?
• How do capacitors store energy, and what factors affect their ability to do so?